Antibodies that bind peptidoglycan recognition protein 1

ABSTRACT

Disclosed herein is a method for identifying TREM-1&#39;s ligand and antibodies, or fragments thereof, which are capable of modifying the function of TREM-1&#39;s ligand. Antibodies that reduce or block TREM-1 activation may be identified and selected using this method. Antibodies that bind to TREM-1&#39;s ligand and reduce TREM-1 activity may be suitable for use as medicaments.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No. 14/376,968, filed Aug. 6, 2014, now issued as U.S. Pat. No. 9,663,568, which is a 371 of International Application PCT/EP2012/074093, filed Nov. 30, 2012, which claims benefit of U.S. Provisional Application 61/598,968, filed Feb. 15, 2012, EP 12158974.1, filed Mar. 12, 2012, and U.S. Provisional Application 61/672,799, filed Jul. 18, 2012; the contents of all above-named applications are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to the field of immunology. More particularly, the present invention relates to a method for the identification of the ligand that is able to stimulate Triggering Receptor Expressed on Myeloid cells (TREM-1), as well as antibodies that bind TREM-1's ligand. Such antibodies are capable of modulating myeloid cell activation and, therefore, inflammatory responses.

BACKGROUND

Peptidoglycan recognition protein 1 (otherwise known as PGLYRP1, PGRP-S, TNFSF3L, PGRP, TAG7 and PGRPS) is expressed in neutrophils and released upon their activation. PGLYRP1 is highly abundant in diseased tissue and has been shown to play an important role in the clearance of bacterial infections by the innate immune system. The family of PGLYRP proteins (PGLYRP1, PGLYRP2, PGLYRP3, PGLYRP4) all interact with bacterial peptidoglycans (PGNs) but there are important differences in the proteins' PGN binding sites. PGLYRP1 has an additional groove hypothesized to constitute a binding site for an unknown effector or signalling protein (J. Mol. Biol. 347:683-691 (2005)). PGLYRP1 is a highly conserved, 196 amino acid long protein consisting of a signal peptide and a peptidoglycan binding domain.

The identification of a signalling mechanism mediated by PGLYRP1 is important in order to understand and thereby manipulate the function of this protein in various infectious and inflammatory diseases.

TREM-1, likewise, has well-described effects in immune modulation but, thus far, the mechanism leading to TREM-1 mediated immune function has not been understood. TREM-1 is a receptor expressed on myeloid cells, such as monocytes, macrophages and neutrophils. It is a transmembrane protein consisting of 234 amino acids, including a single extracellular immunoglobulin domain and a short cytoplasmic tail. TREM-1 has no apparent signalling motif but, when activated, forms dimers/multimers and mediates signalling by associating with the ITAM-containing signalling adaptor protein, DAP12. Downstream signalling may include phosphorylation of Syk and Zap70. Downstream signalling may include activation of the NFAT, ELK, NK-kappaB transcription factor. When TREM-1 is activated, it triggers the release of pro-inflammatory cytokines, such as TNF-α (TNF-alpha), IL-8 and monocyte chemotactic protein-1, from myeloid cells.

TREM-1 is upregulated in patients with sepsis, rheumatoid arthritis (RA) and inflammatory bowel disease (IBD) and increasing evidence supports the theory that TREM-1 contributes to the development and progression of inflammatory diseases. The blocking of TREM-1 signalling has furthermore been shown to have therapeutic activity in in vivo mouse models of RA and IBD.

The mode of action of TREM-1 activation has remained elusive because the ligand that activates TREM-1 is not known in the art. Therefore, there is a need in the art for a means of identifying TREM-1's ligand. There is a need in the art for a method of identifying a molecule, such as an antibody, that is capable of reducing, blocking, or interfering with the interaction of TREM-1 with its ligand. There is a need in the art for a molecule, such as an antibody, that is capable of binding TREM-1's ligand and thus reducing, blocking, or interfering with the stimulation of TREM-1 by its ligand. There is a need in the art for a molecule, such as an antibody, that is capable of binding TREM-1's ligand. There is a need in the art for a molecule, such as an antibody, that is capable of binding TREM-1's ligand and thus blocking TREM-1 activation and signalling. There is a need in the art for a molecule, such as an antibody, that is capable of binding TREM-1's ligand and thus reducing or blocking cytokine release from a myeloid cell expressing TREM-1.

Disclosed herein is a method and assay for identifying TREM-1's ligand and molecules, such as antibodies, that are capable of binding the ligand of TREM-1. Described herein are antibodies that are capable of influencing TREM-1 activation. Thus, the antibodies disclosed herein are suitable for use as pharmaceuticals. Antibodies that bind the ligand of TREM-1 and that reduce or block the interaction of TREM-1 with its ligand may have a substantial impact upon the quality of life of individuals with chronic inflammatory diseases such as rheumatoid arthritis, psoriatic arthritis and inflammatory bowel diseases.

SUMMARY

The invention relates to a method for identifying TREM-1's ligand and molecules, such as antibodies, that bind to TREM-1's ligand, herein identified as being PGLYRP1. The invention also relates to PGLYRP1 antibodies that may be identified by means of the invented method. Thus, the invention relates to PGLYRP1 antibodies that are capable of modifying the activation of TREM-1 by PGLYRP1, such as PGLYRP1 antibodies that are capable of reducing TREM-1 activity (signalling and/or activation) by PGLYRP1. Antibodies that reduce TREM-1 activity may be used for the treatment of inflammation.

The method for identifying a TREM-1 ligand comprises (a) culturing a cell expressing TREM-1, a signalling protein for TREM-1 and a reporter construct that is activated by said signalling protein; (b) detecting, preferably quantifying, the activity of said cell expressing TREM-1 when it is contacted with a cell, a compound or a fluid, such as a biological fluid or a tissue, that triggers TREM-1 activation; (c) contacting the culture of (b) with a TREM-1-activating component; (d) isolating the component that binds TREM-1 and (e) characterising the isolated component. The ligand for TREM-1, identified by means of the current invention as being PGLYRP1, may be used to modify the activity of TREM-1.

The method for identifying a molecule that specifically binds PGLYRP1 and that modifies TREM-1 mediated cellular activity, comprises: (a) culturing the cell according to any one of embodiments 1-18; (b) detecting, preferably quantifying, the activity of said cell expressing TREM-1 when it is contacted with PGLYRP1 and, optionally, a multimerisation agent such as PGN; (c) contacting the culture of (b) with a molecule that specifically binds PGLYRP1; and (d) detecting, preferably quantifying, that the activity of said cell expressing TREM-1 is less than or more than its activity as measured in (b).

The method for identifying a PGLYRP1 antibody that modifies TREM-1 mediated cellular activity comprises: (a) culturing a cell expressing TREM-1, a signalling protein for TREM-1 and a reporter construct that is activated by said signalling protein; (b) detecting, preferably quantifying, the activity of said cell expressing TREM-1 when it is contacted with PGLYRP1 and, optionally, in combination with a multimerising agent such as PGN; (c) contacting the culture of (b) with an antibody that binds PGLYRP1; and (d) detecting, preferably quantifying, that the activity of said cell expressing TREM-1 is less than or more than its activity as measured in (b).

One method of identifying a PGLYRP1 antibody that decreases TREM-1 mediated cellular activity comprises: (a) culturing a cell such as a T-cell expressing TREM-1, a signalling protein such as DAP12 and a reporter gene such as luciferase or beta-galactosidase; (b) incubating said cell with an activated neutrophil and, optionally, in combination with a multimerising agent such as PGN (c) detecting, preferably quantifying, the luminescence of said cell; (d) contacting the culture of the cell and the activated neutrophil with a PGLYRP1 antibody; and (e) detecting, preferably quantifying, that the luminescence of said cell is less than the activity measured in (c).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows that neutrophils activate the BWZ-TREM-1 reporter cell line. The BWZ reporter cell line expresses human TREM-1 and mediates activation of a NFAT-linked beta (β)-galactosidase reporter gene that may be quantitated by luminescence using the Beta-Glo Assay System kit from Promega, Denmark. The figure illustrates activation of the reporter cell line when cultured with neutrophils in the presence of either cytokine cocktails containing TNF-alpha (α), IL-6, IFN-gamma (γ) and GM-CSF or Toll-like Receptor (TLR) activating ‘cocktails’ (TLRL and TLR2 mix (tlrl-kit2hm, Invivogen, Sigma-Aldrich, Denmark), as well as in the presence of separate components of these activation mixtures.

FIGS. 2A-2D show the flow cytometric staining of PGN-stimulated neutrophils with a TREM-1-tetramer recombinant protein. Control protein does not bind (FIG. 2A), whereas a TREM-1-tetramer (SEQ ID NO: 2) binds to a subset of PGN-activated neutrophils (FIG. 2B), and this can be competed by another TREM-1 protein (FIG. 2D) but not by a control protein (FIG. 2C), confirming the specificity of the interaction.

FIG. 3A and FIG. 3B: PGLYRP1 is identified by Immunoprecipitation (IP)/Mass spectroscopy (MS) with TREM-1. Soluble TREM-Fc was incubated with PGN-activated neutrophils, crosslinked, immunoprecipitated followed by cleanup, trypsin digestion and mass spectroscopy. The immunoprecipitation of the TREM-1 binding proteins resulted in 3 specific proteins, 73 proteins overlap with the control protein, and 72 were precipitated by the control protein alone (background (FIG. 3A)). The table (FIG. 3B) shows the results from the TREM-1 specific immunoprecipitation and subsequent mass spectroscopy.

FIG. 4A and FIG. 4B show that soluble TREM-1 binds to PGLYRP1. Shown both by flow cytometric staining with TREM-1 on HEK293 transfectants expressing recombinant PGLYRP1 (FIG. 4A) and by Biacore and ForteBio analyses of the interaction between PGLYRP1 and a TREM-1 tetramer (SEQ ID NO: 2). Soluble human PGLYRP1 bound immobilized human TREM-1 in the presence and absence of 10 μg/ml soluble E. coli peptidoglycan (a PGN) (FIG. 4B). PGN by itself also bound immobilized human PGLYRP1 (FIG. 4C), and soluble human TREM-1 bound to immobilized PGLYRP1 before and after the PGLYRP1 surface was exposed to and bound by PGN (FIG. 4D).

FIG. 5A and FIG. 5B show activation of a TREM-1 reporter cell line by recombinant PGLYRP1. Stimulation of a TREM-1 reporter cell line with recombinant PGLYRP1 (cat. no. 2590-PG-050 R&D Systems Minneapolois Minn., USA), as well as PGLYRP1 generated in-house (SEQ ID NO: 1) leads to a dose dependent response in the presence of PGN (FIG. 5A). This PGLYRP1-induced response can be specifically blocked by TREM-1-Fc fusion protein (FIG. 5B) validating a TREM-1 specific signal.

FIGS. 6A-6G show that monoclonal anti-PGLYRP1 antibodies can block the TREM-1 response in the reporter assay stimulated with PGN-activated neutrophils. Examples of antibody hybridoma clone supernatants screened in various plates for their ability to block the activation signal. A few antibodies (those below the dotted line, such as F10, F95) are able to block this signal. Black dots represent isotype control in each plate (FIG. 6A). FIG. 6B shows testing from another fusion given rise to 2 additional blocking PGLYRP1 antibodies M-hPGRPS-2F5 and -2F7. Testing of commercially available anti-PGLYRP1 mAbs show that they are not able to block this signal even at high doses, whereas the polyclonal, commercially available PGLYRP1 pAb (AF2590, R&D Systems Minneapolois Minn., USA) can. FIG. 6C shows a comparison of the commercially available anti-PGLYRP1 mAb 188C424 from Thermo Scientific (Thermo Scientific, Waltham Mass., USA) with an isotype control (MAB002) and the polyclonal anti-PGLYRP1 pAb (AF2590). FIG. 6D shows a comparison of the commercially available anti-PGLYRP1 mAb 4H230 (US Biological, Salem Mass., USA) with an isotype control (MAB002) and the polyclonal anti-PGLYRP1 pAb (AF2590). FIG. 6E shows a comparison of the commercially available anti-PGLYRP1 mAb 9A319 (US Biological, Salem Mass., USA) with an isotype control (MAB002) and the polyclonal anti-PGLYRP1 pAb (AF2590), FIG. 6F shows a comparison of the commercially available anti-PGLYRP1 mAb 6D653 (Santa Cruz Biotechnology, Santa Cruz Calif., USA) with an isotype control (MAB002) and the polyclonal anti-PGLYRP1 pAb (AF2590). The slight decrease in activity seen for the SC 6D653 mAb appears to be due to the azide-containing formulation since a PGLYRP1 independent signal triggering TREM-1 with 1 ug/ml platebound anti-TREM-1 mAb shows the same phenomenon (FIG. 6G).

FIG. 7 shows that the TREM-1 ligand present in human RA synovial fluid is able to stimulate TREM-1.

-   -   FIG. 7 shows that plate-bound agonistic anti-TREM-1 mAb (R&D         MAB1278, Minneapolis, Minn., USA) stimulates TREM-1 (star) and         that an RA synovial fluid (SF) sample to which PGN has been         added displayed hTREM-1 ligand activity which can be neutralized         by a PGLYRP1 polyclonal antibody (AF2590), indicating that         TREM-1 activity is PGLYRP1 dependent.

FIG. 8 shows the overall structure of the Type II PGLYPRI construct. IC represents the intracellular domain, TM the transmembrane domain—both of which originate from MDL-1 protein sequence, in combination with EC (extracellular) domain of hPGLYRP1.

BRIEF DESCRIPTION OF THE SEQUENCES

SEQ ID NO: 1 represents the amino acid sequence of mature, full length hPGLYRP1 peptide sequence.

SEQ ID NO: 2 represents a recombinant protein sequence containing the following elements: human TREM-1 ECD, linker peptide, human TREM-1 ECD, human allotype IgG1 Fc with 7 mutations differing from wild type. (L15A, L16E, G18A, A111S, P112S, D137E, L139M)

SEQ ID NO: 3 represents human allotype IgG1 Fc with 5 mutations differing from wild type: L15A, L16E, G18A, A111S, P112S.

SEQ ID NO: 4 represents a recombinant protein sequence containing the following elements from N to C terminus: 6×HIS tag, two copies of the streptavidin binding protein domain (SBP), GS linker, C terminus of cartilage oligomeric protein (COMP), GS linker, hDCIR-ECD.

SEQ ID NO: 5 represents a recombinant protein sequence containing the following elements: hTREM-1-ECD, GS linker, C terminus of cartilage oligomeric protein (COMP), GS linker, two copies of the streptavidin binding protein domain (SBP), 6×HIS tag.

SEQ ID NO: 6 represents a recombinant protein sequence containing the following elements in order from N to C terminus, human CD83 ECD, G4Sx3 linker peptide, human CD83 ECD, human allotype IgG1 Fc mutant.

SEQ ID NO: 7 represents full length human PGLYRP1 coding cDNA sequence with C terminal GPI signal sequence. This sequence was cloned into pcDNA3.1zeo(+) (Invitrogen: V860-20, Carlsbad, Calif., USA) via EcoR1 and Xho1 restriction sites.

SEQ ID NO: 8 represents mature full length hTREM-1 ECD (aa. 21-200).

SEQ ID NO: 9 represents cDNA for a CD33 leader tandem hTREM extracellular domains separated by a G4Sx3 linker. A synthetic cDNA with a 5′ EcoRI restriction site, a GCCACC Kozak sequence the CD33 leader sequence followed by the extracellular domain of human TREM-1 (aa17-200) with a interspaced KpnI restriction site and glycine-glycine-glycine-serine spacer repeated three times (G4Sx3) followed by an additional copy of the extracellular domain of human TREM-1 (aa17-200) and an Apa1 site to allow cloning.

SEQ ID NO: 10 represents pentameric hTREM-COMP-SBP38x2-6HIS. EcoR1 site and Kozak are 5′ and BamH1 site is 3′ of ORF.

SEQ ID NO: 11 represents hCD83 tetramer cloned into pJSV002-hFc6mut vector with EcoR1 and Apa1. EcoR1 site and Kozak are 5′ and Apa1 site is 3′ of ORF.

SEQ ID NO: 12 represents pentameric 6HIS-SBP38x2-COMP-hDCIR. EcoR1 site and Kozak 5′ and BamH1 3′ of ORF.

SEQ ID NO: 13 represents the nucleic acid sequence of the variable heavy chain of a monoclonal PGLYRP1 antibody (1F36, mAb 0182).

SEQ ID NO: 14 represents the nucleic acid sequence of the variable light chain of a monoclonal PGLYRP1 antibody (1F36, mAb 0182).

SEQ ID NO: 15 represents the amino acid sequence of the variable heavy chain of a monoclonal PGLYRP1 antibody (1F36, mAb 0182).

SEQ ID NO: 16 represents the amino acid sequence of the variable light chain of a monoclonal PGLYRP1 antibody (1F36, mAb 0182).

SEQ ID NO: 17 represents the nucleic acid sequence of the variable heavy chain of a monoclonal PGLYRP1 antibody (1F10).

SEQ ID NO: 18 represents the nucleic acid sequence of the variable light chain of a monoclonal PGLYRP1 antibody (1F10).

SEQ ID NO: 19 represents the amino acid sequence of the variable heavy chain of a monoclonal PGLYRP1 antibody (1F10).

SEQ ID NO: 20 represents the amino acid sequence of the variable light chain of a monoclonal PGLYRP1 antibody (1F10).

SEQ ID NO: 21 represents the nucleic acid sequence of the variable heavy chain of a monoclonal PGLYRP1 antibody (1F105, mAb 0184).

SEQ ID NO: 22 represents the nucleic acid sequence of the variable light chain of a monoclonal PGLYRP1 antibody (1F105, mAb 0184).

SEQ ID NO: 23 represents the amino acid sequence of the variable heavy chain of a monoclonal PGLYRP1 antibody (1F105, mAb 0184).

SEQ ID NO: 24 represents the amino acid sequence of the variable light chain of a monoclonal PGLYRP1 antibody (1F105, mAb 0184).

SEQ ID NO: 25 represents the nucleic acid sequence of the variable heavy chain of a monoclonal PGLYRP1 antibody (1F95).

SEQ ID NO: 26 represents the nucleic acid sequence of the variable light chain of a monoclonal PGLYRP1 antibody (1F95).

SEQ ID NO: 27 represents the amino acid sequence of the variable heavy chain of a monoclonal PGLYRP1 antibody (1F95).

SEQ ID NO: 28 represents the amino acid sequence of the variable light chain of a monoclonal PGLYRP1 antibody (1F95).

SEQ ID NO: 29 represents the nucleic acid sequence of the variable heavy chain of a monoclonal PGLYRP1 antibody (2F5).

SEQ ID NO: 30 represents the nucleic acid sequence of the variable light chain of a monoclonal PGLYRP1 antibody (2F5).

SEQ ID NO: 31 represents the amino acid sequence of the variable heavy chain of a monoclonal PGLYRP1 antibody (2F5).

SEQ ID NO: 32 represents the amino acid sequence of the variable light chain of a monoclonal PGLYRP1 antibody (2F5).

SEQ ID NO: 33 represents the nucleic acid sequence of the variable heavy chain of a monoclonal PGLYRP1 antibody (2F7).

SEQ ID NO: 34 represents the nucleic acid sequence of the variable light chain of a monoclonal PGLYRP1 antibody (2F7).

SEQ ID NO: 35 represents the amino acid sequence of the variable heavy chain of a monoclonal PGLYRP1 antibody (2F7).

SEQ ID NO: 36 represents the amino acid sequence of the variable light chain of a monoclonal PGLYRP1 antibody (2F7).

SEQ ID NO: 37 represents the amino acid sequence of Type II 1.0 PGLYRP1.

SEQ ID NO: 38 represents the amino acid sequence of Type II 2.0 PGLYRP1.

SEQ ID NO: 39 represents the amino acid sequence of an epitope tag.

SEQ ID NO: 40 represents the amino acid sequence of full-length human PGLYRP2.

SEQ ID NO: 41 represents the amino acid sequence of full-length human PGLYRP3.

SEQ ID NO: 42 represents the amino acid sequence of full-length human PGLYRP4.

SEQ ID NO: 43 represents the nucleic acid sequence of hCD33-hTreml ECD(aa17-200)-Fc6mut.

SEQ ID NO: 44 represents the amino acid sequence of hCD33-hTreml ECD(aa17-200)-Fc6mut.

SEQ ID NO: 45 represents the nucleic acid sequence for hCD33-hTremL1 ECD(aa16-162)-Fc6mut.

SEQ ID NO: 46 represents the amino acid sequence of hCD33-hTremL1 ECD(aa16-162)-Fc6mut.

SEQ ID NO: 47 represents the nucleic acid sequence for hCD33-hTremL2 ECD(aa19-268)-Fc6mut.

SEQ ID NO: 48 represents the amino acid sequence of hCD33-hTremL2 ECD(aa19-268)-Fc6mut

SEQ ID NO: 49 represents the nucleic acid sequence of hCD33-hTREM2-Fc6mut dimer

SEQ ID NO: 50 represents the amino acid sequence of the hCD33-hTREM2-Fc6mut dimer.

SEQ ID NO: 51 represents the nucleic acid sequence of a primer.

SEQ ID NO: 52 represents the nucleic acid sequence of a primer.

SEQ ID NO: 53 represents the amino acid sequence of hCD33.

DESCRIPTION

The invention relates to a method for the identification of molecules such as antibodies that are capable of specifically binding TREM-1's signalling partner, herein identified as being PGLYRP1, and influencing PGLYRP1 binding with its signalling partner, TREM-1. PGLYRP1 may be used to modify the activity of TREM-1. Hence, the invention relates to molecules, such as antibodies, that influence inflammatory responses that are mediated by PGLYRP1. Antibodies that are capable of binding to PGLYRP1 and that influence TREM-1 activation and signalling have been created and identified.

A method or assay for the identification of TREM-1's ligand and for identification of molecules, such as antibodies, that are capable of specifically binding PGLYRP1 and reducing or blocking PGLYRP1 activation of TREM-1 may be created as follows:

A first cell or population of first cells is transfected with genes encoding TREM-1 or fragments thereof, a signalling protein and a reporter construct. The cell may be of haematopoietic origin, such as a myeloid cell, it may be a T-cell or it may be any other cell type that is capable of being transfected and expressing such molecules. The signalling protein may be any protein that is capable of transmitting or conveying a signal, either directly or indirectly, from TREM-1 to the reporter construct and may include DAP10, DAP12, TCR zeta, Fc gammaRIII, an Fc receptor, or any other protein that is capable of transmitting or conveying a signal from TREM-1 to the reporter construct. Alternatively, the signalling protein may be a TREM-1/signalling chimera molecule. The reporter construct comprises a transcription factor and a reporter gene, which in turn encodes a reporter protein that produces a detectable signal, such as a quantifiable signal. The transcription factor may be NFAT or NFkB or any other suitable transcription factor known in the art. The reporter gene may encode beta (β)-galactosidase, luciferase, green fluorescent protein (GFP), chloramphenicol transferase or any other reporter protein capable of producing a detectable signal. One suitable cell line that may be used for this bioassay is the BWZ.36/hTREM-1:DAP12:NFAT-LacZ T-cell (herein also identified as the “BWZ/hTREM-1 reporter cell”), the creation of which is described in detail in the examples. When activated, the BWZ/hTREM-1 reporter cell produces beta (β)-galactosidase, the production of which may be measured using equipment or kits known in the art, such as Beta Glow™ (Promega E4720, Madison, Wis., USA).

The first cell or population of first cells may be activated by incubation with PGLYRP1 and, optionally, a multimerisation agent. The optional multimerisation agent acts as a scaffold for PGLYRP1 and may be peptidoglycan (PGN), neutrophil extracellular traps (NETs), hyaloronic acid, a proteoglycan structure such as versican, aggrecan, decorin or fibrin, or any other naturally occurring matrix structure or molecule that is able to multimerise or present PGLYRP1. The first cell may be activated by incubation with one or more second cell(s) that express PGLYRP1 on its/their surface, or intracellularly. An example of intracellular expression may be the storage of PGLYRP1 in secretory granules. The second cell may thus be any cell (or population of cells) that expresses or is transfected with a gene encoding PGLYRP1 and that expresses PGLYRP1 on its surface. Such a second cell may be a prokaryotic or a eukaryotic cell, such as a mammalian cell, such as a CHO cell, a BHK cell or a HEK cell. The second cell may also be an activated neutrophil. Neutrophils may be obtained from the whole blood or tissue of an individual and used either in bulk or as purified neutrophils. Any agent that mimics the bacterial activation of neutrophils, such as peptidoglycan (PGN) from the cell wall of a bacterium, such as PGN-SA, PGN-EB, PGN-EC, PGN-BS (InVivogen, tlrl-pgnsa, SanDiego, Calif.), may be used to activate a neutrophil.

The activity of the first cell or population of first cells is then detected and, preferably, measured.

The culture of the first cell and the second cell(s) expressing PGLYRP1 and/or the culture of the first cell incubated with PGLYRP1 and, optionally, a multimerisation agent such as PGN, is contacted with an antibody that has been raised against PGLYRP1. The activity of the first cell or population of first cells is detected, and preferably measured.

In this way, antibodies that are capable of binding TREM-1's ligand, PGLYRP1, and that influence the interaction of PGLYRP1 with TREM-1 may be identified. PGLYRP1 antibodies that cause an increase in the activity of the first cell enhance the interaction of PGLYRP1 with TREM-1 and are herein identified as “stimulating PGLYRP1 antibodies”. PGLYRP1 antibodies that cause a decrease in the activity of the first cell reduce, interfere, or block the interaction of PGLYRP1 with TREM-1 and are herein identified as “inhibitory PGLYRP1 antibodies”. Inhibitory PGLYRP1 antibodies reduce or block TREM-1 activation and signalling.

Hence, the present invention relates to a method of characterising the function of PGLYRP1 antibodies. Antibodies capable of specifically binding PGLYRP1 and that have any effect upon TREM-1 activation and downstream signalling are herein referred to as “functional PGLYRP1 antibodies”. Consequently, the term “functional PGLYRP1 antibodies” is intended to encompass both stimulating PGLYRP1 antibodies and inhibitory PGLYRP1 antibodies.

Furthermore, the present invention relates to antibodies that are capable of specifically binding PGLYRP1 and reducing, interfering with, or blocking its interaction with TREM-1, hence reducing TREM-1 activation and downstream signalling. Antibodies of the invention may have an immunoregulatory function, reducing the cytokine production of myeloid cells expressing TREM-1. For example, antibodies of the invention may reduce or prevent release of TNF-alpha (α), IL-1beta (b), IL-6, IFN-gamma (γ), MIP-1beta (b), MCP-1, IL-8 and/or GM-CSF from myeloid cells such as macrophages and/or neutrophils and/or myeloid cells in diseased tissue such as synovial tissue. Antibodies of the invention may be capable of down-regulating neutrophil responses.

PGLYRP1 antibodies according to the invention may reduce or block TREM-1 activation by means of one or a combination of several different mechanisms, affecting TREM-1 directly or indirectly. Antibodies of the invention may prevent PGLYRP1 from creating a functional complex with TREM-1.

Antibodies of the invention may block PGLYRP1 function by reducing or blocking TREM-1 activation and downstream signalling.

The present invention also relates to inhibitory PGLYRP1 antibodies that may be identified by other means than the method disclosed herein.

Antibodies of the invention may be capable of binding both human PGLYRP1 and PGLYRP1 from a species other than a human being. The term “PGLYRP1”, as used herein, thus encompasses any naturally occurring form of PGLYRP1 which may be derived from any suitable organism, such as an invertebrate species or a vertebrate species. PGLYRP1 for use as described herein may be vertebrate PGLYRP1, such as mammalian PGLYRP1, such as PGLYRP1 from a primate (such as a human, a chimpanzee, a cynomolgus monkey or a rhesus monkey); a rodent (such as a mouse or a rat), a lagomorph (such as a rabbit), or an artiodactyl (such a cow, sheep, pig or camel), among others. Preferably, the PGLYRP1 is human PGLYRP1 (SEQ ID NO: 1). The PGLYRP1 may be a mature form of PGLYRP1 such as a PGLYRP1 protein that has undergone post-translational processing within a suitable cell. Such a mature PGLYRP1 protein may, for example, be glycosylated. The PGLYRP1 may be a full length PGLYRP1 protein. The PGLYRP1 may be a splice variant.

Antibodies of the invention may also be capable of specifically binding variants of PGLYRP1 such as SEQ ID NO: 37 (Type II 1.0 PGLYRP1) and/or SEQ ID NO: 38 (Type II 1.0 PGLYRP1).

Antibodies of the invention may be capable of influencing, such as inhibiting/reducing/blocking, the activity (signalling and/or activation) of both human TREM-1 and TREM-1 from another species than a human being. The term “TREM-1”, as used herein, thus encompasses any naturally occurring form of TREM-1 which may be derived from any suitable organism. For example, TREM-1 for use as described herein may be vertebrate TREM-1, such as mammalian TREM-1, such as TREM-1 from a primate (such as a human, a chimpanzee, a cynomolgous monkey or a rhesus monkey); a rodent (such as a mouse or a rat), a lagomorph (such as a rabbit), or an artiodactyl (such a cow, sheep, pig or camel), among others. Preferably, the TREM-1 is human TREM-1. The TREM-1 may be a mature form of TREM-1 such as a TREM-1 protein that has undergone post-translational processing within a suitable cell. Such a mature TREM-1 protein may, for example, be glycosylated. The TREM-1 may be a full length TREM-1 protein. The TREM-1 may be a splice variant.

The term “antibody” herein refers to a protein, derived from a germline immunoglobulin sequence, which is capable of specifically binding to PGLYRP1 or a portion thereof. The term includes full length antibodies of any isotype (that is, IgA, IgE, IgG, IgM and/or IgY) and any single chain or fragment thereof. An antibody that specifically binds to PGLYRP1, or portion thereof, may bind exclusively to PGLYRP1, or portion thereof, or it may bind to a limited number of homologous antigens, or portions thereof.

Antibodies of the invention may be monoclonal antibodies, in the sense that they may be directly or indirectly derived from a single clone of a B lymphocyte. An antibody of the invention may be a monoclonal antibody, with the proviso that it is not 188C424 (Thermo Scientific), 4H230 or 9A319 (US Biological) or Clone 6D653 (Santa Cruz Biotechnology).

Antibodies of the current invention may be isolated. The term “isolated antibody” refers to an antibody that has been separated and/or recovered from another/other component(s) of its natural environment and/or purified from a mixture of components in its natural environment.

Antibodies may be recombinantly expressed in prokaryotic cells, eukaryotic cells or an acellular system derived from cellular extracts. The prokaryotic cell may be E. coli. The eukaryotic cell may be a yeast, insect or mammalian cell, such as a cell derived from an organism that is a primate (such as a human, a chimpanzee, a cynomolgus monkey or a rhesus monkey), a rodent (such as a mouse or a rat), a lagomorph (such as a rabbit) or an artiodactyl (such a cow, sheep, pig or camel). Suitable mammalian cell lines include, but are not limited to, HEK293 cells, CHO cells and HELA cells. PGLYRP1 antibodies may also be produced by means of other methods known to the person skilled in the art, such as a phage display or a yeast display. Antibodies of the invention may be raised in vivo by immunising a suitable mammal with PGLYRP1, a cell expressing PGLYRP1 or a combination of both.

PGLYRP1 antibodies may be produced, screened and purified using, for example, the methods described in the Examples. In brief, any suitable mouse, including a PGLYRP1 knock-out (KO) mouse or a TREM-1 KO mouse, may be immunised with PGLYRP1, a cell expressing PGLYRP1 or a combination of both. Primary screening of hybridoma supernatants may be performed using direct ELISA or FMAT and secondary screening may be performed using flow cytometry. Positive hybridoma supernatants, as well as purified antibodies, may then be screened for binding to, for example, full length PGLYRP1. Positive hybridoma supernatants or purified antibodies may then be tested for their ability to reduce or block PGLYRP1-stimulation of TREM-1-bearing cells. The method of the current invention may be used for this purpose.

Full-length antibodies of the invention may comprise at least four polypeptide chains: that is, two heavy (H) chains and two light (L) chains that are interconnected by disulfide bonds. One immunoglobulin sub-class of particular pharmaceutical interest is the IgG family, which may be sub-divided into isotypes IgG1, IgG2, IgG3 and IgG4. IgG molecules are composed of two heavy chains, interlinked by two or more disulfide bonds, and two light chains, each attached to a heavy chain by a disulfide bond. A heavy chain may comprise a heavy chain variable region (VH) and up to three heavy chain constant (CH) regions: CH1, CH2 and CH3. A light chain may comprise a light chain variable region (VL) and a light chain constant region (CL). VH and VL regions can be further subdivided into regions of hypervariability, termed complementarity determining regions (CDRs), interspersed with regions that are more conserved, termed framework regions (FR). VH and VL regions are typically composed of three CDRs and four FRs, arranged from amino-terminus to carboxy-terminus in the following order: FR1, CDR1, FR2, CDR2, FR3, CDR3, FR4. The hypervariable regions of the heavy and light chains form a [binding] domain that is capable of interacting with an antigen (PGLYRP1), whilst the constant region of an antibody may mediate binding of the immunoglobulin to host tissues or factors, including but not limited to various cells of the immune system (effector cells), Fc receptors and the first component (Clq) of the classical complement system.

Examples of antigen-binding fragments include Fab, Fab′, F(ab)₂, F(ab′)₂, F(ab)S, Fv (typically the VL and VH domains of a single arm of an antibody), single-chain Fv (scFv; see e.g. Bird et al., Science 1988; 242:42S-426; and Huston et al. PNAS 1988; 85:5879-5883), dsFv, Fd (typically the VH and CHI domain), and dAb (typically a VH domain) fragments; VH, VL, VhH, and V-NAR domains; monovalent molecules comprising a single VH and a single VL chain; minibodies, diabodies, triabodies, tetrabodies, and kappa bodies (see, e.g., III et al. Protein Eng 1997; 10: 949-57); camel IgG; IgNAR; as well as one or more isolated CDRs or a functional paratope, where the isolated CDRs or antigen-binding residues or polypeptides can be associated or linked together so as to form a functional antibody fragment. Various types of antibody fragments have been described or reviewed in, e.g., Holliger and Hudson, Nat Biotechnol 2005; 2S: 1126-1136; WO2005040219, and published U.S. Patent Applications 20050238646 and 20020161201.

Certain antigen-binding fragments of antibodies may be suitable in the context of the current invention, as it has been shown that the antigen-binding function of an antibody can be performed by fragments of a full-length antibody. The term “antigen-binding fragment” of an antibody refers to one or more fragments of an antibody that retain the ability to specifically bind to an antigen, such as human PGLYRP1 or PGLYRP1 from another species, as described herein. Examples of antigen-binding fragments include Fab, Fab′, F(ab)₂, F(ab′)₂, F(ab)S, Fv (typically the VL and VH domains of a single arm of an antibody), single-chain Fv (scFv; see e.g. Bird et al., Science 1988; 242:42S-426; and Huston et al. PNAS 1988; 85:5879-5883), dsFv, Fd (typically the VH and CHI domain), and dAb (typically a VH domain) fragments; VH, VL, VhH, and V-NAR domains; monovalent molecules comprising a single VH and a single VL chain; minibodies, diabodies, triabodies, tetrabodies, and kappa bodies (see, e.g., III et al. Protein Eng 1997; 10:949-57); camel IgG; IgNAR; as well as one or more isolated CDRs or a functional paratope, where the isolated CDRs or antigen-binding residues or polypeptides can be associated or linked together so as to form a functional antibody fragment. Various types of antibody fragments have been described or reviewed in, e.g., Holliger and Hudson, Nat Biotechnol 2005; 2S:1126-1136; WO2005040219, and published U.S. Patent Applications 20050238646 and 20020161201. These antibody fragments may be obtained using conventional techniques known to those of skill in the art, and the fragments may be screened for utility in the same manner as intact antibodies.

An antibody of the invention may be a human antibody or a humanised antibody. The term “human antibody”, as used herein, is intended to include antibodies having variable regions in which at least a portion of a framework region and/or at least a portion of a CDR region are derived from human germline immunoglobulin sequences. (For example, a human antibody may have variable regions in which both the framework and CDR regions are derived from human germline immunoglobulin sequences.) Furthermore, if the antibody contains a constant region, the constant region is also derived from human germline immunoglobulin sequences. The human antibodies of the invention may include amino acid residues not encoded by human germline immunoglobulin sequences (e.g., mutations introduced by random or site-specific mutagenesis in vitro or by somatic mutation in vivo).

Such a human antibody may be a human monoclonal antibody. Such a human monoclonal antibody may be produced by a hybridoma which includes a B cell obtained from a transgenic nonhuman animal, e.g., a transgenic mouse, having a genome comprising a human heavy chain transgene and a light chain transgene fused to an immortalized cell.

Human antibodies may be isolated from sequence libraries built on selections of human germline sequences, further diversified with natural and synthetic sequence diversity.

Human antibodies may be prepared by in vitro immunisation of human lymphocytes followed by transformation of the lymphocytes with Epstein-Barr virus.

The term “human antibody derivative” refers to any modified form of the human antibody, such as a conjugate of the antibody and another agent or antibody.

The term “humanised antibody”, as used herein, refers to a human/non-human chimeric antibody that contains one or more sequences (CDR regions) derived from a non-human immunoglobulin. A humanised antibody is, thus, a human immunoglobulin (recipient antibody) in which at least residues from a hypervariable region of the recipient are replaced by residues from a hypervariable region of a non-human species (donor antibody) such as from a mouse, rat, rabbit, or non-human primate, which have the desired specificity, affinity, and capacity. In some instances, FR residues of the human immunoglobulin are replaced by corresponding non-human residues. An example of such a modification is the introduction of one or more so-called back-mutations.

Furthermore, humanised antibodies may comprise residues that are not found in the recipient antibody or in the donor antibody. These modifications are made to further refine antibody performance. In general, a humanised antibody will comprise at least one—typically two—variable domains, in which all or substantially all of the CDR regions correspond to those of a non-human immunoglobulin and in which all or substantially all of the FR residues are those of a human immunoglobulin sequence. The humanised antibody can, optionally, also comprise at least a portion of an immunoglobulin constant region (Fc), typically that of a human immunoglobulin.

The term “humanised antibody derivative” refers to any modified form of the humanised antibody, such as a conjugate of the antibody and another agent or antibody.

The term “chimeric antibody”, as used herein, refers to an antibody whose light and heavy chain genes have been constructed, typically by genetic engineering, from immunoglobulin variable and constant region genes that originate from different species. For example, the variable segments of genes from a mouse monoclonal antibody may be joined to human constant segments.

The fragment crystallisable region (“Fc region”/“Fc domain”) of an antibody is the N-terminal region of an antibody, which comprises the constant CH2 and CH3 domains. The Fc domain may interact with cell surface receptors called Fc receptors, as well as some proteins of the complement system. The Fc region enables antibodies to interact with the immune system. In one aspect of the invention, antibodies may be engineered to include modifications within the Fc region, typically to alter one or more of its functional properties, such as serum half-life, complement fixation, Fc-receptor binding, protein stability and/or antigen-dependent cellular cytotoxicity, or lack thereof, among others. Furthermore, an antibody of the invention may be chemically modified (e.g., one or more chemical moieties can be attached to the antibody) or be modified to alter its glycosylation, again to alter one or more functional properties of the antibody. Preferably, a modified Fc domain comprises one or more, and perhaps all of the following mutations that will result in decreased affinity to certain Fc receptors (L234A, L235E, and G237A) and in reduced C1q-mediated complement fixation (A330S and P331S), respectively (residue numbering according to the EU index).

The isotype of an antibody of the invention may be IgG, such as IgG1, such as IgG2, such as IgG4. If desired, the class of an antibody may be “switched” by known techniques. For example, an antibody that was originally produced as an IgM molecule may be class switched to an IgG antibody. Class switching techniques also may be used to convert one IgG subclass to another, for example: from IgG1 to IgG2 or IgG4; from IgG2 to IgG1 or IgG4; or from IgG4 to IgG1 or IgG2. Engineering of antibodies to generate constant region chimeric molecules, by combination of regions from different IgG subclasses, can also be performed.

In one embodiment, the hinge region of CH1 is modified such that the number of cysteine residues in the hinge region is altered, e.g., increased or decreased. This approach is described further for instance in U.S. Pat. No. 5,677,425 by Bodmer et al.

The constant region may further be modified to stabilise the antibody, e.g., to reduce the risk of a bivalent antibody separating into two monovalent VH-VL fragments. For example, in an IgG4 constant region, residue S241 may be mutated to a proline (P) residue to allow complete disulphide bridge formation at the hinge (see, e.g., Angal et al., Mollmmunol. 199S; 30:105-8).

Antibodies or fragments thereof may also be defined in terms of their complementarity-determining regions (CDRs). The term “complementarity-determining region” or “hypervariable region”, when used herein, refers to the regions of an antibody in which amino acid residues involved in antigen binding are situated. The CDRs are generally comprised of amino acid residues 24-34 (L1), 50-56 (L2) and 89-97 (L3) in the light-chain variable domain and 31-35 (H1), 50-65 (H2) and 95-102 (H3) in the heavy-chain variable domain; (Kabat et al. (1991) Sequences of Proteins of Immunological Interest, Fifth Edition, U.S. Department of Health and Human Services, NIH Publication No. 91-3242) and/or those residues from a “hypervariable loop” (residues 26-32 (L1), 50-52 (L2) and 91-96 (L3) in the light-chain variable domain and 26-32 (H1), 53-55 (H2) and 96-101 (H3) in the heavy-chain variable domain; Chothia and Lesk, J. Mol. Biol 1987; 196:901-917). Typically, the numbering of amino acid residues in this region is performed by the method described in Kabat et al., supra. Phrases such as “Kabat position”, “Kabat residue”, and “according to Kabat” herein refer to this numbering system for heavy chain variable domains or light chain variable domains. Using the Kabat numbering system, the actual linear amino acid sequence of a peptide may contain fewer or additional amino acids corresponding to a shortening of, or insertion into, a framework (FR) or CDR of the variable domain. For example, a heavy chain variable domain may include amino acid insertions (residue 52a, 52b and 52c according to Kabat) after residue 52 of CDR H2 and inserted residues (e.g. residues 82a, 82b, and 82c, etc., according to Kabat) after heavy chain FR residue 82. The Kabat numbering of residues may be determined for a given antibody by alignment at regions of homology of the sequence of the antibody with a “standard” Kabat numbered sequence.

The term “framework region” or “FR” residues refer to those VH or VL amino acid residues that are not within the CDRs, as defined herein.

An antibody of the invention may comprise a CDR region from one or more of the specific antibodies disclosed herein, such as a CDR region from within SEQ ID NOs: 15, 16, 19, 20, 23, 24, 27, 28, 31, 32, 35 or 36.

The 1F36 antibody has a heavy chain as shown in SEQ ID NO: 15 and a light chain as shown in SEQ ID NO: 16. An antibody of the invention may comprise this variable heavy chain sequence and/or this variable light chain sequence. The 1F36 antibody has the CDR sequences shown at amino acids 31 to 35, 50 to 66 and 99 to 108 of SEQ ID NO: 15 and amino acids 24 to 34, 51 to 56 and 89 to 97 of SEQ ID NO: 16. An antibody of the invention may comprise 1, 2, 3, 4, 5 or all 6 of these CDR sequences.

An antibody according to the invention may comprise: a CDRH1 sequence that corresponds to amino acid residues 31 to 35 (SYWMN) of SEQ ID NO: 15, wherein one of these amino acid residues may be substituted by a different amino acid residue; and/or a CDRH2 sequence that corresponds to amino acids 50 to 66 (MIHPSDSETRLNQKFKD) of SEQ ID NO: 15, wherein one, two or three of these amino acids may be substituted by a different amino acid residue; and/or a CDRH3 sequence that corresponds to amino acid residues 99 to 108 (DYSDYDGFAY]) of SEQ ID NO: 15, wherein one, two or three of these amino acid residues may be substituted by a different amino acid.

An antibody according to the invention may comprise: a CDRL1 sequence that corresponds to amino acid residues 24 to 34 (RASQSISDYLH) of SEQ ID NO: 16, wherein one, two or three of these amino acid residues may be substituted with a different amino acid; and/or a CDRL2 sequence that corresponds to amino acid residues 51 to 56 (ASQSIS) of SEQ ID NO: 16, wherein one or two of these amino acid residues may be substituted with a different amino acid; and/or a CDRL3 sequence that corresponds to amino acid residues 89 to 97 (QNGHSFPLT) of SEQ ID NO: 16, wherein one or two of these amino acid residues may be substituted with a different amino acid.

The 1F10 antibody has a heavy chain as shown in SEQ ID NO: 19 and a light chain as shown in SEQ ID NO: 20. An antibody of the invention may comprise this variable heavy chain sequence and/or this variable light chain sequence. The 1F10 antibody has the CDR sequences shown at amino acids 31 to 35, 50 to 66 and 99 to 109 of SEQ ID NO: 19 and amino acids 24 to 33, 49 to 55 and 88 to 96 of SEQ ID NO: 20. An antibody of the invention may comprise 1, 2, 3, 4, 5 or all 6 of these CDR sequences.

An antibody according to the invention may comprise: a CDRH1 sequence that corresponds to amino acid residues 31 to 35 (DYNMY) of SEQ ID NO: 19, wherein one of these amino acid residues may be substituted by a different amino acid residue; and/or a CDRH2 sequence that corresponds to amino acids 50 to 66 (YIDPYNGDTSYNQKFKG) of SEQ ID NO: 19, wherein one, two or three of these amino acids may be substituted by a different amino acid residue; and/or a CDRH3 sequence that corresponds to amino acid residues 99 to 109 (GDYGNPFYLDY) of SEQ ID NO: 19, wherein one, two or three of these amino acid residues may be substituted by a different amino acid.

An antibody according to the invention may comprise a CDRL1 sequence that corresponds to amino acid residues 24 to 33 (SVSSSVNYMY) of SEQ ID NO: 20, wherein one, two or three of these amino acid residues may be substituted with a different amino acid; and/or a CDRL2 sequence that corresponds to amino acid residues 49 to 55 (DTSKLPS) of SEQ ID NO: 20, wherein one or two of these amino acid residues may be substituted with a different amino acid; and/or a CDRL3 sequence that corresponds to amino acid residues 88 to 96 (QQWTSNPPT) of SEQ ID NO: 20, wherein one or two of these amino acid residues may be substituted with a different amino acid.

The 1F105 antibody has a heavy chain as shown in SEQ ID NO: 23 and a light chain as shown in SEQ ID NO: 24. An antibody of the invention may comprise this variable heavy chain sequence and/or this variable light chain sequence. The 1F105 antibody has the CDR sequences shown at amino acids 31 to 35, 50 to 66 and 99 to 108 of SEQ ID NO: 23 and amino acids 24 to 33, 49 to 55 and 88 to 96 of SEQ ID NO: 24. An antibody of the invention may comprise 1, 2, 3, 4, 5 or all 6 of these CDR sequences.

An antibody according to the invention may comprise: a CDRH1 sequence that corresponds to amino acid residues 31 to 35 (DTYIH) of SEQ ID NO: 23, wherein one of these amino acid residues may be substituted by a different amino acid residue; and/or a CDRH2 sequence that corresponds to amino acids 50 to 66 (RIDPANDDTKYDPNFQG) of SEQ ID NO: 23, wherein one, two or three of these amino acids may be substituted by a different amino acid residue; and/or a CDRH3 sequence that corresponds to amino acid residues 99 to 108 (SDNSDSWFAY) of SEQ ID NO: 23, wherein one, two or three of these amino acid residues may be substituted by a different amino acid.

An antibody according to the invention may comprise: a CDRL1 sequence that corresponds to amino acid residues 24 to 33 (SVSSSVNFMN) of SEQ ID NO: 24, wherein one, two or three of these amino acid residues may be substituted with a different amino acid; and/or a CDRL2 sequence that corresponds to amino acid residues 49 to 55 (DTSKLAP) of SEQ ID NO: 24, wherein one or two of these amino acid residues may be substituted with a different amino acid; and/or a CDRL3 sequence that corresponds to amino acid residues 88 to 96 (HQWSSYSLT) of SEQ ID NO: 24, wherein one or two of these amino acid residues may be substituted with a different amino acid.

The 1F95 antibody has a heavy chain as shown in SEQ ID NO: 27 and a light chain as shown in SEQ ID NO: 28. An antibody of the invention may comprise this variable heavy chain sequence and/or this variable light chain sequence. The 1F95 antibody has the CDR sequences shown at amino acids 31 to 35, 50 to 66 and 99 to 106 of SEQ ID NO: 27 and amino acids 24 to 33, 49 to 54 and 87 to 95 of SEQ ID NO: 28. An antibody of the invention may comprise 1, 2, 3, 4, 5 or all 6 of these CDR sequences.

An antibody according to the invention may comprise: a CDRH1 sequence that corresponds to amino acid residues 31 to 35 (DYNMH) of SEQ ID NO: 27, wherein one of these amino acid residues may be substituted by a different amino acid residue; and/or a CDRH2 sequence that corresponds to amino acids 50 to 66 (YVDPYDGGTSSNQKFKG) of SEQ ID NO: 27, wherein one, two or three of these amino acids may be substituted by a different amino acid residue; and/or a CDRH3 sequence that corresponds to amino acid residues 99 to 106 (EVPYYFDY) of SEQ ID NO: 27, wherein one, two or three of these amino acid residues may be substituted by a different amino acid.

An antibody according to the invention may comprise: a CDRL1 sequence that corresponds to amino acid residues 24 to 33 (VASSSVTYMY) of SEQ ID NO: 28, wherein one, two or three of these amino acid residues may be substituted with a different amino acid; and/or a CDRL2 sequence that corresponds to amino acid residues 49 to 54 (THPLAS) of SEQ ID NO: 28, wherein one or two of these amino acid residues may be substituted with a different amino acid; and/or a CDRL3 sequence that corresponds to amino acid residues 87 to 95 (PHWNTNPPT) of SEQ ID NO: 28, wherein one or two of these amino acid residues may be substituted with a different amino acid.

The 2F5 antibody has a heavy chain as shown in SEQ ID NO: 31 and a light chain as shown in SEQ ID NO: 32. An antibody of the invention may comprise this variable heavy chain sequence and/or this variable light chain sequence. The 2F5 antibody has the CDR sequences shown at amino acids 31 to 35, 50 to 66 and 99 to 109 of SEQ ID NO: 31 and amino acids 24 to 33, 49 to 55 and 88 to 96 of SEQ ID NO: 32. An antibody of the invention may comprise 1, 2, 3, 4, 5 or all 6 of these CDR sequences.

An antibody according to the invention may comprise: a CDRH1 sequence that corresponds to amino acid residues 31 to 35 (DYYMY) of SEQ ID NO: 31, wherein one of these amino acid residues may be substituted by a different amino acid residue; and/or a CDRH2 sequence that corresponds to amino acids 50 to 66 (AISDDSTYTYYPDSVKG) of SEQ ID NO: 31, wherein one, two or three of these amino acids may be substituted by a different amino acid residue; and/or a CDRH3 sequence that corresponds to amino acid residues 99 to 109 (GGYGNLYAMDY) of SEQ ID NO: 31, wherein one, two or three of these amino acid residues may be substituted by a different amino acid.

An antibody according to the invention may comprise: a CDRL1 sequence that corresponds to amino acid residues 24 to 35 (TASSSVSSSYLH) of SEQ ID NO: 32, wherein one, two or three of these amino acid residues may be substituted with a different amino acid; and/or a CDRL2 sequence that corresponds to amino acid residues 51-57 (STSNLAS) of SEQ ID NO: 32, wherein one or two of these amino acid residues may be substituted with a different amino acid; and/or a CDRL3 sequence that corresponds to amino acid residues 90-98 (HQYHRSPFT) of SEQ ID NO: 32, wherein one or two of these amino acid residues may be substituted with a different amino acid.

The 2F7 antibody has a heavy chain as shown in SEQ ID NO: 35 and a light chain as shown in SEQ ID NO: 36. An antibody of the invention may comprise this variable heavy chain sequence and/or this variable light chain sequence. The 2F5 antibody has the CDR sequences shown at amino acids 31 to 35, 50 to 66 and 99 to 109 of SEQ ID NO: 35 and amino acids 24 to 34, 50 to 56 and 89 to 96 of SEQ ID NO: 36. An antibody of the invention may comprise 1, 2, 3, 4, 5 or all 6 of these CDR sequences.

An antibody according to the invention may comprise: a CDRH1 sequence that corresponds to amino acid residues 31 to 35 (NYVMH) of SEQ ID NO: 35, wherein one of these amino acid residues may be substituted by a different amino acid residue; and/or a CDRH2 sequence that corresponds to amino acids 50 to 66 (WINPFNDGTNYNENFKN) of SEQ ID NO: 35, wherein one, two or three of these amino acids may be substituted by a different amino acid residue; and/or a CDRH3 sequence that corresponds to amino acid residues 99 to 109 (SGFITTLIEDY) of SEQ ID NO: 35, wherein one, two or three of these amino acid residues may be substituted by a different amino acid.

An antibody according to the invention may comprise: a CDRL1 sequence that corresponds to amino acid residues 24 to 34 (KASESVGSFVS) of SEQ ID NO: 36, wherein one, two or three of these amino acid residues may be substituted with a different amino acid; and/or a CDRL2 sequence that corresponds to amino acid residues 50 to 56 (GASNRYT) of SEQ ID NO: 36, wherein one or two of these amino acid residues may be substituted with a different amino acid; and/or a CDRL3 sequence that corresponds to amino acid residues 89 to 96 (GQYYTHPT) of SEQ ID NO: 36, wherein one or two of these amino acid residues may be substituted with a different amino acid.

The term “antigen” (Ag) refers to the molecular entity used to immunise an immunocompetent vertebrate to produce the antibody (Ab) that recognizes the Ag. Herein, Ag is termed more broadly and is generally intended to include target molecules that are specifically recognized by the Ab, thus including fragments or mimics of the molecule used in the immunization process, or other process, e.g. phage display, used for generating the Ab.

The term “epitope”, as used herein, is defined in the context of a molecular interaction between an “antigen binding polypeptide”, such as an antibody (Ab), and its corresponding antigen (Ag). Generally, “epitope” refers to the area or region on an Ag to which an Ab specifically binds, i.e. the area or region in physical contact with the Ab. Physical contact may be defined using various criteria (e.g., a distance cut-off of 2-6 Å, such as 3 Å, such as 4 Å, such as 5 Å; or solvent accessibility) for atoms in the Ab and Ag molecules. A protein epitope may comprise amino acid residues in the Ag that are directly involved in binding to a Ab (also called the immunodominant component of the epitope) and other amino acid residues, which are not directly involved in binding, such as amino acid residues of the Ag which are effectively blocked by the Ab, i.e. amino acid residues within the “solvent-excluded surface” and/or the “footprint” of the Ab.

The term epitope herein comprises both types of binding region in any particular region of PGLYRP1 that specifically binds to a PGLYRP1 antibody. PGLYRP1 may comprise a number of different epitopes, which may include, without limitation, conformational epitopes which consist of one or more non-contiguous amino acids located near each other in the mature PGLYRP1 conformation and post-translational epitopes which consist, either in whole or part, of molecular structures covalently attached to PGLYRP1, such as carbohydrate groups. PGLYRP1 may also comprise linear epitopes.

The epitope for a given antibody (Ab)/antigen (Ag) pair can be described and characterized at different levels of detail using a variety of experimental and computational epitope mapping methods. The experimental methods include mutagenesis, X-ray crystallography, Nuclear Magnetic Resonance (NMR) spectroscopy, Hydrogen deuterium eXchange Mass Spectrometry (HX-MS) and various competition binding methods; methods that are known in the art. As each method relies on a unique principle, the description of an epitope is intimately linked to the method by which it has been determined. Thus, depending on the epitope mapping method employed, the epitope for a given Ab/Ag pair may be described differently.

At its most detailed level, the epitope for the interaction between the Ag and the Ab can be described by the spatial coordinates defining the atomic contacts present in the Ag-Ab interaction, as well as information about their relative contributions to the binding thermodynamics. At a less detailed level, the epitope can be characterized by the spatial coordinates defining the atomic contacts between the Ag and Ab. At an even less detailed level the epitope can be characterized by the amino acid residues that it comprises as defined by a specific criteria such as the distance between or solvent accessibility of atoms in the Ab:Ag complex. At a further less detailed level the epitope can be characterized through function, e.g. by competition binding with other Abs. The epitope can also be defined more generically as comprising amino acid residues for which substitution by another amino acid will alter the characteristics of the interaction between the Ab and Ag.

In the context of an X-ray derived crystal structure defined by spatial coordinates of a complex between an Ab, e.g. a Fab fragment, and its Ag, the term epitope is herein, unless otherwise specified or contradicted by context, specifically defined as PGLYRP1 residues characterized by having a heavy atom (i.e. a non-hydrogen atom) within a distance of, eg., 2-6 Å, such as 3 Å, such as 4 Å, such as 5 Å from a heavy atom in the Ab.

From the fact that descriptions and definitions of epitopes, dependent on the epitope mapping method used, are obtained at different levels of detail, it follows that comparison of epitopes for different Abs on the same Ag can similarly be conducted at different levels of detail.

Epitopes described at the amino acid level, e.g. determined from an X-ray structure, are said to be identical if they contain the same set of amino acid residues. Epitopes are said to overlap if at least one amino acid is shared by the epitopes. Epitopes are said to be separate (unique) if no amino acid residue are shared by the epitopes.

The definition of the term “paratope” is derived from the above definition of “epitope” by reversing the perspective. Thus, the term “paratope” refers to the area or region on the Ab to which an Ag specifically binds, i.e. with which it makes physical contact to the Ag.

In the context of an X-ray derived crystal structure, defined by spatial coordinates of a complex between an Ab, such as a Fab fragment, and its Ag, the term paratope is herein, unless otherwise specified or contradicted by context, specifically defined as Ag residues characterized by having a heavy atom (i.e. a non-hydrogen atom) within a distance of 4 Å from a heavy atom in PGLYRP1.

The epitope and paratope for a given antibody (Ab)/antigen (Ag) pair may be identified by routine methods. For example, the general location of an epitope may be determined by assessing the ability of an antibody to bind to different fragments or variant PGLYRP1 polypeptides. The specific amino acids within PGLYRP1 that make contact with an antibody (epitope) and the specific amino acids in an antibody that make contact with PGLYRP1 (paratope) may also be determined using routine methods. For example, the antibody and target molecule may be combined and the Ab:Ag complex may be crystallised. The crystal structure of the complex may be determined and used to identify specific sites of interaction between the antibody and its target.

Antibodies that bind to the same antigen can be characterised with respect to their ability to bind to their common antigen simultaneously and may be subjected to “competition binding”/“binning”. In the present context, the term “binning” refers to a method of grouping antibodies that bind to the same antigen. “Binning” of antibodies may be based on competition binding of two antibodies to their common antigen in assays based on standard techniques such as surface plasmon resonance (SPR), ELISA or flow cytometry.

An antibody's “bin” is defined using a reference antibody. If a second antibody is unable to bind to an antigen at the same time as the reference antibody, the second antibody is said to belong to the same “bin” as the reference antibody. In this case, the reference and the second antibody competitively bind the same part of an antigen and are coined “competing antibodies”. If a second antibody is capable of binding to an antigen at the same time as the reference antibody, the second antibody is said to belong to a separate “bin”. In this case, the reference and the second antibody do not competitively bind the same part of an antigen and are coined “non-competing antibodies”.

Antibody “binning” does not provide direct information about the epitope. Competing antibodies, i.e. antibodies belonging to the same “bin” may have identical epitopes, overlapping epitopes or even separate epitopes. The latter is the case if the reference antibody bound to its epitope on the antigen takes up the space required for the second antibody to contact its epitiope on the antigen (“steric hindrance”). Non-competing antibodies generally have separate epitopes.

An antibody according to the current invention may be capable of competing with 1F10 for binding to PGLYRP1. An antibody according to the current invention may be capable of competing with 1F36/mAb 0182 for binding to PGLYRP1. An antibody according to the current invention may be capable of competing with 1F95 for binding to PGLYRP1. An antibody according to the current invention may be capable of competing with 1F105/mAb 0184 for binding to PGLYRP1. An antibody according to the current invention may be capable of competing with 2F5 for binding to PGLYRP1. An antibody according to the current invention may be capable of competing with 2F7 for binding to PGLYRP1. Hence, an antibody according to the current invention may belong to the same bin as any one or more of these antibodies.

The term “binding affinity” herein refers to a measurement of the strength of a non-covalent interaction between two molecules, e.g. an antibody, or fragment thereof, and an antigen. The term “binding affinity” is used to describe monovalent interactions (intrinsic activity).

Binding affinity between two molecules, e.g. an antibody, or fragment thereof, and an antigen, through a monovalent interaction may be quantified by determining the equilibrium dissociation constant (K_(D)). In turn, K_(D) can be determined by measurement of the kinetics of complex formation and dissociation, e.g. by the SPR method. The rate constants corresponding to the association and the dissociation of a monovalent complex are referred to as the association rate constant k_(a) (or k_(on)) and dissociation rate constant k_(d) (or k_(off)), respectively. K_(D) is related to k_(a) and k_(d) through the equation K_(D)=k_(d)/k_(a).

Following the above definition, binding affinities associated with different molecular interactions, such as comparison of the binding affinity of different antibodies for a given antigen, may be compared by comparison of the K_(D) values for the individual antibody/antigen complexes.

A PGLYRP1 antibody of the invention may have a K_(D) for its target (PGLYRP1) of 1×10⁻⁶M or less, 1×10⁻⁷M or less, 1×10⁻⁸M or less, or 1×10⁻⁹M or less, or 1×10⁻¹⁰M or less, 1×10⁻¹¹M or less, 1×10⁻¹²M or less or 1×10⁻¹³M or less.

An antibody according to the current invention may be able to compete with another molecule, such as a naturally occurring ligand or receptor or another antibody, for binding to PGLYRP1. Therefore, an antibody according to the current invention may be able to bind PGLYRP1 with a greater affinity that that of another molecule also capable of binding PGLYRP1. The ability of an antibody to compete with a natural ligand/receptor for binding to an antigen may be assessed by determining and comparing the K_(D) value for the interactions of interest, such as a specific interaction between an antibody and an antigen, with that of the K_(D) value of an interaction not of interest.

The term “binding specificity” herein refers to the interaction of a molecule such as an antibody, or fragment thereof, with a single exclusive antigen, or with a limited number of highly homologous antigens (or epitopes). Antibodies that are capable of specifically binding to PGLYRP1 are not capable of binding dissimilar molecules. Antibodies according to the invention may not be able to bind PGLYRP family members such as PGLYRP2, PGLYRP3 and PGLYRP4. Antibodies according to the invention may not be able to bind human PGLYRP family members such as human PGLYRP2, human PGLYRP3 and human PGLYRP4.

The specificity of an interaction and the value of an equilibrium binding constant can be determined directly by well-known methods. Standard assays to evaluate the ability of ligands (such as antibodies) to bind their targets are known in the art and include, for example, ELISAs, Western blots, RIAs, and flow cytometry analysis. The binding kinetics and binding affinity of the antibody also can be assessed by standard assays known in the art, such as SPR.

A competitive binding assay can be conducted in which the binding of the antibody to the target is compared to the binding of the target by another ligand of that target, such as another antibody.

In another aspect, the present invention provides compositions and formulations comprising molecules of the invention, such as the PGLYRP1 antibodies, polynucleotides, vectors and cells described herein. For example, the invention provides a pharmaceutical composition that comprises one or more PGLYRP1 antibodies of the invention, formulated together with a pharmaceutically acceptable carrier.

Accordingly, one object of the invention is to provide a pharmaceutical formulation comprising such a PGLYRP1 antibody which is present in a concentration from 0.25 mg/ml to 250 mg/ml, and wherein said formulation has a pH from 2.0 to 10.0. The formulation may further comprise one or more of a buffer system, a preservative, a tonicity agent, a chelating agent, a stabiliser, or a surfactant, as well as various combinations thereof. The use of preservatives, isotonic agents, chelating agents, stabilisers and surfactants in pharmaceutical compositions is well-known to the skilled person. Reference may be made to Remington: The Science and Practice of Pharmacy, 19^(th) edition, 1995.

In one embodiment, the pharmaceutical formulation is an aqueous formulation. Such a formulation is typically a solution or a suspension, but may also include colloids, dispersions, emulsions, and multi-phase materials. The term “aqueous formulation” is defined as a formulation comprising at least 50% w/w water. Likewise, the term “aqueous solution” is defined as a solution comprising at least 50% w/w water, and the term “aqueous suspension” is defined as a suspension comprising at least 50% w/w water.

In another embodiment, the pharmaceutical formulation is a freeze-dried formulation, to which the physician or the patient adds solvents and/or diluents prior to use.

In a further aspect, the pharmaceutical formulation comprises an aqueous solution of such an antibody, and a buffer, wherein the antibody is present in a concentration from 1 mg/ml or above, and wherein said formulation has a pH from about 2.0 to about 10.0.

The PGLYRP1 antibodies of the present invention and pharmaceutical compositions comprising such antibodies may be used for the treatment of inflammatory diseases such as the following: inflammatory bowel disease (IBD), Crohns disease (CD), ulcerative colitis (UC), irritable bowel syndrome, rheumatoid arthritis (RA), psoriasis, psoriatic arthritis, systemic lupus erythematosus (SLE), lupus nephritis, type I diabetes, Grave's disease, multiple sclerosis (MS), autoimmune myocarditis, Kawasaki disease, coronary artery disease, chronic obstructive pulmonary disease, interstitial lung disease, autoimmune thyroiditis, scleroderma, systemic sclerosis, osteoarthritis, atoptic dermatitis, vitiligo, graft versus host disease, Sjogrens's syndrome, autoimmune nephritis, Goodpasture's syndrome, chronic inflammatory demyelinating polyneuropathy, allergy, asthma and other autoimmune diseases that are a result of either acute or chronic inflammation. The PGLYRP1 antibodies of the present invention and pharmaceutical compositions comprising such antibodies may be used for the treatment of cardiovascular disease, stroke, ischemia reperfusion injury, pneumonia, sepsis and cancer.

PGLYRP1 antibodies of the invention are suitable for use in the treatment of individuals with inflammatory bowel disease. Inflammatory Bowel Disease (IBD) is a disease that may affect any part of the gastrointestinal tract from mouth to anus, causing a wide variety of symptoms. IBD primarily causes abdominal pain, diarrhea (which may be bloody), vomiting, or weight loss, but may also cause complications outside of the gastrointestinal tract such as skin rashes, arthritis, inflammation of the eye, fatigue, and lack of concentration. Patients with IBD can be divided into two major classes, those with ulcerative colitis (UC) and those with Crohn's disease (CD). While CD generally involves the ileum and colon, it can affect any region of the intestine but is often discontinuous (focused areas of disease spread throughout the intestine), UC always involves the rectum (colonic) and is more continuous. In CD, the inflammation is transmural, resulting in abscesses, fistulas and strictures, whereas in UC, the inflammation is typically confined to the mucosa. There is no known pharmaceutical or surgical cure for Crohn's disease, whereas some patients with UC can be cured by surgical removal of the colon. Treatment options are restricted to controlling symptoms, maintaining remission and preventing relapse. Efficacy in inflammatory bowel disease in the clinic may be measured as a reduction in the Crohn's Disease Activity Index (CDAI) score for CD which is scoring scale based on laboratory tests and a quality of life questionnaire. In animal models, efficacy is mostly measured by increase in weight and also a disease activity index (DAI), which is a combination of stool consistency, weight and blood in stool.

PGLYRP1 antibodies of the invention are suitable for use in the treatment of individuals with rheumatoid arthritis. Rheumatoid arthritis (RA) is a systemic disease that affects nearly if not all of the body and is one of the most common forms of arthritis. It is characterized by inflammation of the joint, which causes pain, stiffness, warmth, redness and swelling. This inflammation is a consequence of inflammatory cells invading the joints, and these inflammatory cells release enzymes that may digest bone and cartilage. As a result, this inflammation can lead to severe bone and cartilage damage and to joint deterioration and severe pain amongst other physiologic effects. The involved joint can lose its shape and alignment, resulting in pain and loss of movement.

There are several animal models for rheumatoid arthritis known in the art. For example, in the collagen-induced arthritis (CIA) model, mice develop an inflammatory arthritis that resembles human rheumatoid arthritis. Since CIA shares similar immunological and pathological features with RA, this makes it a suitable model for screening potential human anti-inflammatory compounds. Efficacy in this model is measured by decrease in joint swelling. Efficacy in RA in the clinic is measured by the ability to reduce symptoms in patients which is measured as a combination of joint swelling, erythrocyte sedimentation rate, C-reactive protein levels and levels of serum factors, such as anti-citrullinated protein antibodies.

PGLYRP1 antibodies of the invention are suitable for use in the treatment of individuals with psoriasis. Psoriasis is a T-cell mediated inflammatory disorder of the skin that can cause considerable discomfort. It is a disease for which there is currently no cure and affects people of all ages. Although individuals with mild psoriasis can often control their disease with topical agents, more than one million patients worldwide require ultraviolet light treatments or systemic immunosuppressive therapy. Unfortunately, the inconvenience and risks of ultraviolet radiation and the toxicities of many therapies limit their long-term use. Moreover, patients usually have recurrence of psoriasis, and in some cases rebound shortly after stopping immunosuppressive therapy. A recently developed model of psoriasis based on the transfer of CD4+ T cells mimics many aspects of human psoriasis and therefore can be used to identify compounds suitable for use in treatment of psoriasis (Davenport et al., Internat. Immunopharmacol 2: 653-672, 2002). Efficacy in this model is a measured by reduction in skin pathology using a scoring system. Similarly, efficacy in patients is measured by a decrease in skin pathology.

PGLYRP1 antibodies of the invention are suitable for use in the treatment of individuals with psoriatic arthritis. Psoriatic arthritis (PA) is a type of inflammatory arthritis that occurs in a subset of patients with psoriasis. In these patients, the skin pathology/symptoms are accompanied by joint swelling, similar to that seen in rheumatoid arthritis. It features patchy, raised, red areas of skin inflammation with scaling. Psoriasis often affects the tips of the elbows and knees, the scalp, the navel and around the genital areas or anus. Approximately 10% of patients who have psoriasis also develop an associated inflammation of their joints.

The term “treatment”, as used herein, refers to the medical therapy of any human or other animal subject in need thereof. Said subject is expected to have undergone physical examination by a medical or veterinary medical practitioner, who has given a tentative or definitive diagnosis which would indicate that the use of said treatment is beneficial to the health of said human or other animal subject. The timing and purpose of said treatment may vary from one individual to another, according to many factors, such as the status quo of the subject's health. Thus, said treatment may be prophylactic, palliative, symptomatic and/or curative.

In terms of the present invention, prophylactic, palliative, symptomatic and/or curative treatments may represent separate aspects of the invention.

An antibody of the invention may be administered parenterally, such as intravenously, such as intramuscularly, such as subcutaneously. Alternatively, an antibody of the invention may be administered via a non-parenteral route, such as perorally or topically. An antibody of the invention may be administered prophylactically. An antibody of the invention may be administered therapeutically (on demand).

EXEMPLARY EMBODIMENTS

1. A cell expressing TREM-1, a signalling protein for TREM-1 and a reporter construct that is activated by said signalling protein.

2. The cell according to embodiment 1, wherein the cell is of haematopoetic origin.

3. The cell according to embodiment 2, wherein the cell is a myeloid cell.

4. The cell according to embodiment 2, wherein the cell is a T-cell.

5. The cell according to any one of embodiments 1-4, wherein the signalling protein is DAP10.

6. The cell according to any one of embodiments 1-4, wherein the signalling protein is DAP12.

7. The cell according to any one of embodiments 1-4, wherein the signalling protein is TCR zeta.

8. The cell according to any one of embodiments 1-4, wherein the signalling protein is Fc gamma RIII.

9. The cell according to any one of embodiments 1-4, wherein the signalling protein is a Fc receptor.

10. The cell according to any one of embodiments 1-9, wherein the reporter construct comprises a transcription factor and a reporter gene.

11. The cell according to embodiment 10, wherein said transcription factor is NFAT.

12. The cell according to embodiment 11, wherein said transcription factor is NFkB.

13. The cell according to any one of embodiments 10-12, wherein said reporter gene encodes β-galactosidase.

14. The cell according to any one of embodiments 10-12, wherein said reporter gene encodes luciferase.

15. The cell according to any one of embodiments 10-12, wherein said reporter gene encodes green fluorescent protein (GFP).

16. The cell according to any one of embodiments 10-12, wherein said reporter gene is a gene that encodes chloramphenicol transferase.

17. The cell according to any one of embodiments 1-4, 6, 10-11 and 13, which is a BWZ.36/hTREM-1:DAP12:NFAT-LacZ T-cell.

18. A method of stimulating the cell according to any one of embodiments 1-17, comprising contacting said cell with PGLYRP1.

19. A method of stimulating the cell according to any one of embodiments 1-17, comprising contacting said cell with PGLYRP1 and PGN.

20. The method according to any one of embodiments 18-19, wherein said PGLYRP1 is expressed by a cell.

21. The method according to embodiment 20, wherein the cell expressing PGLYRP1 is a prokaryotic cell.

22. The method according to embodiment 20, wherein the cell expressing PGLYRP1 is a eukaryotic cell.

23. The method according to embodiment 22, wherein the cell expressing PGLYRP1 is a mammalian cell.

24. The method according to embodiment 23, wherein the cell expressing PGLYRP1 is an activated neutrophil.

25. The method according to embodiment 23, wherein the cell expressing PGLYRP1 is a HEK cell.

26. A method of identifying a TREM-1 ligand, comprising: (a) culturing the cell according to any one of embodiments 1-18; (b) detecting, preferably quantifying, the activity of said cell expressing TREM-1 when it is contacted with a cell, a fluid such as a biological fluid or a tissue that triggers TREM-1 activation; (c) contacting the culture of (b) with a TREM-1 protein; (d) isolating the component that binds TREM-1 and (e) characterising the isolated component. 27. A method of identifying a molecule that specifically binds PGLYRP1 and that modifies TREM-1 mediated cellular activity, comprising: (a) culturing the cell according to any one of embodiments 1-18; (b) detecting, preferably quantifying, the activity of said cell expressing TREM-1 when it is contacted with PGLYRP1 and, optionally, a multimerisation agent such as PGN; (c) contacting the culture of (b) with a molecule that specifically binds PGLYRP1; and (d) detecting, preferably quantifying, that the activity of said cell expressing TREM-1 is less than or more than its activity as measured in (b). 28. A method of identifying a PGLYRP1 antibody, or fragment thereof, that modifies TREM-1 mediated cellular activity, comprising: (a) culturing the cell according to any one of embodiments 1-18; (b) detecting, preferably quantifying, the activity of said cell expressing TREM-1 when it is contacted with PGLYRP1 and, optionally, a multimerisation agent such as PGN; (c) contacting the culture of (b) with an antibody that binds PGLYRP1; and (d) detecting, preferably quantifying, that the activity of said cell expressing TREM-1 is less than or more than its activity as measured in (b). 29. The method according to embodiment 27, wherein said PGLYRP1 antibody, or fragment thereof, decreases TREM-1 mediated cellular activity and wherein the activity of the first cell when measured in (d) is less than its activity when measured in (b). 30. The method according to embodiment 27, wherein said PGLYRP1 antibody, or fragment thereof, increases TREM-1 mediated cellular activity and wherein the activity of the first cell when measured in (d) is more than its activity when measured in (b). 31. The PGLYRP1 antibody or fragment thereof that is identified by means of the method according to any one of embodiments 28-30. 32. A PGLYRP1 antibody or fragment thereof which is capable of specifically binding PGLYRP1 and reducing PGLYRP1-mediated TREM-1 activity. 33. The antibody, or fragment thereof, according to any one of embodiments 31-32, which is capable of reducing the release of one or more cytokines from cells that express TREM-1. 34. The antibody or fragment thereof according to any one of embodiments 31-33, which is a monoclonal antibody. 35. The antibody or fragment thereof according to any one of embodiments 31-34, which is a humanised antibody. 36. The antibody or fragment thereof according to any one of embodiments 31-34, which is a human antibody. 37. The antibody or fragment thereof according to any one of embodiments 31-34, which is a chimeric antibody. 38. The antibody according to any one of embodiments 31-37, wherein the isotype of said antibody is IgG. 39. The antibody according to embodiment 38, wherein said isotype is IgG1, IgG2 or IgG4. 40. The antibody according to embodiment 37, wherein the isotype of said antibody is IgG1. 41. The antibody according to embodiment 37, wherein the isotype of said antibody is IgG4. 42. The antibody or fragment thereof according to any one of embodiments 31-41, which is capable of competing with antibody 1F10 for binding to PGLYRP1. 43. The antibody or fragment thereof according to any one of embodiments 31-41, which is capable of competing with antibody 1F36/mAb 0182 for binding to PGLYRP1. 44. The antibody or fragment thereof according to any one of embodiments 31-41, which is capable of competing with antibody 1F95 for binding to PGLYRP1. 45. The antibody according to any one of embodiments 31-41, which is capable of competing with antibody 1F105/mAb 0184 for binding to PGLYRP1. 46. The antibody according to any one of embodiments 31-41, which is capable of competing with antibody 2F5 for binding to PGLYRP1. 47. The antibody according to any one of embodiments 31-41, which is capable of competing with antibody 2F7 for binding to PGLYRP1. 48. The antibody or fragment thereof according to any one of embodiments 31-47, which is capable of specifically binding SEQ ID NO: 37 (Type II 1.0 PGLYRP1) and/or SEQ ID NO: 38 (Type II 2.0 PGLYRP1). 49. The antibody or fragment thereof according to any one of embodiments 31-48, which has a K_(D) for its target that is 1×10⁻⁶M or less, 1×10⁻⁷M or less, 1×10⁻⁸M or less, or 1×10⁻⁹M or less, or 1×10⁻¹⁰M or less, 1×10⁻¹¹M or less, 1×10⁻¹²M or less or 1×10⁻¹³M or less, when determined using surface plasmon resonance. 50. The antibody according to any one of embodiments 31-49, the heavy chain of which comprises: a CDRH1 sequence corresponding to amino acid residues 31 to 35 (SYWMN) of SEQ ID NO: 15, wherein one of said amino acid residues may be substituted by a different amino acid residue; and/or a CDRH2 sequence corresponding to amino acids 50 to 66 (MIHPSDSETRLNQKFKD) of SEQ ID NO: 15, wherein one, two or three of said amino acids may be substituted by a different amino acid residue; and/or a CDRH3 sequence corresponding to amino acid residues 99 to 108 (DYSDYDGFAY]) of SEQ ID NO: 15, wherein one, two or three of said amino acid residues may be substituted by a different amino acid. 51. The antibody according to any one of embodiments 31-49, the heavy chain of which comprises: a CDRH1 sequence corresponding to amino acid residues 31 to 35 (DYNMY) of SEQ ID NO: 19, wherein one of said amino acid residues may be substituted by a different amino acid residue; and/or a CDRH2 sequence corresponding to amino acids 50 to 66 (YIDPYNGDTSYNQKFKG) of SEQ ID NO: 19, wherein one, two or three of said amino acids may be substituted by a different amino acid residue; and/or a CDRH3 sequence corresponding to amino acid residues 99 to 109 (GDYGNPFYLDY) of SEQ ID NO: 19, wherein one, two or three of said amino acid residues may be substituted by a different amino acid. 52. The antibody according to any one of embodiments 31-49, the heavy chain of which comprises: a CDRH1 sequence corresponding to amino acid residues 31 to 35 (DTYIH) of SEQ ID NO: 23, wherein one of said amino acid residues may be substituted by a different amino acid residue; and/or a CDRH2 sequence of amino acids 50 to 66 (RIDPANDDTKYDPNFQG) of SEQ ID NO: 23, wherein one, two or three of said amino acids may be substituted by a different amino acid residue; and/or a CDRH3 sequence of amino acid residues 99 to 108 (SDNSDSWFAY) of SEQ ID NO: 23, wherein one, two or three of said amino acid residues may be substituted by a different amino acid. 53. The antibody according to any one of embodiments 31-49, the heavy chain of which comprises: a CDRH1 sequence corresponding to amino acid residues 31 to 35 (DYNMH) of SEQ ID NO: 27, wherein one of said amino acid residues may be substituted by a different amino acid residue; and/or a CDRH2 sequence corresponding to amino acids 50 to 66 (YVDPYDGGTSSNQKFKG) of SEQ ID NO: 27, wherein one, two or three of said amino acids may be substituted by a different amino acid residue; and/or a CDRH3 sequence corresponding to amino acid residues 99 to 106 (EVPYYFDY) of SEQ ID NO: 27, wherein one, two or three of said amino acid residues may be substituted by a different amino acid. 54. The antibody according to any one of embodiments 31-49, the heavy chain of which comprises: a CDRH1 sequence that corresponds to amino acid residues 31 to 35 (DYYMY) of SEQ ID NO: 31, wherein one of these amino acid residues may be substituted by a different amino acid residue; and/or a CDRH2 sequence that corresponds to amino acids 50 to 66 (AISDDSTYTYYPDSVKG) of SEQ ID NO: 31, wherein one, two or three of these amino acids may be substituted by a different amino acid residue; and/or a CDRH3 sequence that corresponds to amino acid residues 99 to 109 (GGYGNLYAMDY) of SEQ ID NO: 31, wherein one, two or three of these amino acid residues may be substituted by a different amino acid. 55. The antibody according to any one of embodiments 31-49, the heavy chain of which comprises: a CDRH1 sequence that corresponds to amino acid residues 31 to 35 (NYVMH) of SEQ ID NO: 35, wherein one of these amino acid residues may be substituted by a different amino acid residue; and/or a CDRH2 sequence that corresponds to amino acids 50 to 66 (WINPFNDGTNYNENFKN) of SEQ ID NO: 35, wherein one, two or three of these amino acids may be substituted by a different amino acid residue; and/or a CDRH3 sequence that corresponds to amino acid residues 99 to 109 (SGFITTLIEDY) of SEQ ID NO: 35, wherein one, two or three of these amino acid residues may be substituted by a different amino acid. 56. The antibody according to any one of embodiments 50-55, the light chain of which comprises: a CDRL1 sequence corresponding to amino acid residues 24 to 34 (RASQSISDYLH) of SEQ ID NO: 16, wherein one, two or three of said amino acid residues may be substituted with a different amino acid; and/or a CDRL2 sequence corresponding to amino acid residues 51 to 56 (ASQSIS) of SEQ ID NO: 16, wherein one or two of said amino acid residues may be substituted with a different amino acid; and/or a CDRL3 sequence corresponding to amino acid residues 89 to 97 (QNGHSFPLT) of SEQ ID NO: 16, wherein one or two of said amino acid residues may be substituted with a different amino acid. 57. The antibody according to any one of embodiments 50-55, the light chain of which comprises: a CDRL1 sequence corresponding to amino acid residues 24 to 33 (SVSSSVNYMY) of SEQ ID NO: 20, wherein one, two or three of said amino acid residues may be substituted with a different amino acid; and/or a CDRL2 sequence corresponding to amino acid residues 49 to 55 (DTSKLPS) of SEQ ID NO: 20, wherein one or two of said amino acid residues may be substituted with a different amino acid; and/or a CDRL3 sequence corresponding to amino acid residues 88 to 96 (QQVVTSNPPT) of SEQ ID NO: 20, wherein one or two of said amino acid residues may be substituted with a different amino acid. 58. The antibody according to any one of embodiments 50-55, the light chain of which comprises: a CDRL1 sequence corresponding to amino acid residues 24 to 33 (SVSSSVNFMN) of SEQ ID NO: 24, wherein one, two or three of said amino acid residues may be substituted with a different amino acid; and/or a CDRL2 sequence corresponding to amino acid residues 49 to 55 (DTSKLAP) of SEQ ID NO: 24, wherein one or two of said amino acid residues may be substituted with a different amino acid; and/or a CDRL3 sequence corresponding to amino acid residues 88 to 96 (HQWSSYSLT) of SEQ ID NO: 24, wherein one or two of said amino acid residues may be substituted with a different amino acid. 59. The antibody according to any one of embodiments 50-55, the light chain of which comprises: a CDRL1 sequence corresponding to amino acid residues 24 to 33 (VASSSVTYMY) of SEQ ID NO: 28, wherein one, two or three of said amino acid residues may be substituted with a different amino acid; and/or a CDRL2 sequence corresponding to amino acid residues 49 to 54 (THPLAS) of SEQ ID NO: 28, wherein one or two of said amino acid residues may be substituted with a different amino acid; and/or a CDRL3 sequence corresponding to amino acid residues 87 to 95 (PHWNTNPPT) of SEQ ID NO: 28, wherein one or two of said amino acid residues may be substituted with a different amino acid. 60. The antibody according to any one of embodiments 50-55, the light chain of which comprises: a CDRL1 sequence that corresponds to amino acid residues 24 to 35 (TASSSVSSSYLH) of SEQ ID NO: 32, wherein one, two or three of these amino acid residues may be substituted with a different amino acid; and/or a CDRL2 sequence that corresponds to amino acid residues 51-57 (STSNLAS) of SEQ ID NO: 32, wherein one or two of these amino acid residues may be substituted with a different amino acid; and/or a CDRL3 sequence that corresponds to amino acid residues 90-98 (HQYHRSPFT) of SEQ ID NO: 32, wherein one or two of these amino acid residues may be substituted with a different amino acid. 61. The antibody according to any one of embodiments 50-55, the light chain of which comprises: a CDRL1 sequence that corresponds to amino acid residues 24 to 34 (KASESVGSFVS) of SEQ ID NO: 36, wherein one, two or three of these amino acid residues may be substituted with a different amino acid; and/or a CDRL2 sequence that corresponds to amino acid residues 50 to 56(GASNRYT) of SEQ ID NO: 36, wherein one or two of these amino acid residues may be substituted with a different amino acid; and/or a CDRL3 sequence that corresponds to amino acid residues 89 to 96 (GQYYTHPT) of SEQ ID NO: 36, wherein one or two of these amino acid residues may be substituted with a different amino acid. 62. The antibody according to any one of embodiments 31-61 for use as a medicament. 63. The antibody according to any one of embodiments 31-62 for use in the treatment of an inflammatory disease. 64. An antibody that is capable of specifically binding PGLYRP1 and reducing PGLYRP1-mediated TREM-1 activity for use as a medicament. 65. An antibody that is capable of specifically binding PGLYRP1 and reducing PGLYRP1-mediated TREM-1 activity for use in the treatment of an inflammatory disease. 66. Use according to any one of embodiments 62-65, wherein the inflammatory disease is an autoimmune disease. 67. Use according to embodiment 66, wherein the autoimmune disease is rheumatoid arthritis (RA). 68. Use according to embodiment 66, wherein the autoimmune disease is inflammatory bowel disease (IBD) and/or ulcerative colitis. 69. Use according to embodiment 66, wherein the autoimmune disease is psoriatic arthritis (PA). 70. Use according to embodiment 62 or 64 in the treatment of cardiovascular disease, stroke, ischemia reperfusion injury, sepsis and/or cancer.

The present invention is further illustrated by the following examples which should not be construed as further limiting. The contents of all figures and all references, patents and published patent applications cited throughout this application are expressly incorporated herein by reference.

EXAMPLES Example 1: Generation of a BWZ.36 HumanTREM-1:DAP12 Stable Cell Line

The BWZ.36/hTREM-1:DAP12:NFAT-LacZ cell line (herein also referred to as the “BWZ/hTREM-1 reporter cell”) was derived from BW5147 T cells (Mus musculus thymus lymphoma cell line, ATCC TIB-47, LGC Standards, Middelsex, UK) and contains a LacZ reporter construct regulated by four copies of the NFAT promoter element (see Karttunen, J. & Shastri, N. (1991) Proc. Natl. Acad. Sci. USA 88, 3972-3976 and Fiering, S., Northrop, J. P., Nolan, G. P., Matilla, P., Crabtree, G. R. & Herzenberg, L. A. (1990) Genes Dev. 4, 1823-1834). TREM/DAP12/pMX-IRES vector (encoding 786 bp of TREM-1 from a SmaI site to BamHI site using TREM-1 cDNA (Gene Bank Ref. ID: NM_018643.2, Sino Biological Inc., Beijing, China) as template and oligo 5′ TAGTAGGGATCCGCTGGTGCACAGGAAGG (SEQ ID NO: 51) and 5′ TAGTAGGCGGCCGCTTCGTGGGCCTAGGGTAC (SEQ ID NO: 52) as primers cloned into pIREShyg vector GenBank Accession #U89672 (Cat. no. 6061-1, Clontech Laboratories, CA, USA) was transfected in PLAT-E packaging cell line (provided by W. Yokoyama, Washington University; alternatively, Cat. no. RV-101, Cell Biolabs Inc, Bio-Mediator KY, Vantaa, Finland) using Superfect transfection reagent (Cat. no. 301305, Qiagen Nordic, Denmark). PLAT-E supernatants containing TREM/DAP12/pMX-IRES viral particles were used to infect BWZ.36 cells as follows: 2×10⁵ BWZ.36 cells were cultured in 6 well plates and the medium was replaced with 1.5 ml of supernatant containing the viral particles +8 mg/ml of polybrene. After 6-8 hours, 1.5 ml of normal medium was added to the plate and the cells were incubated for an additional 24 hours. BWZ.36 cell lines stably expressing TREM-1 were stained with anti TREM-1 monoclonal antibody (clone 21C7; Bouchon et al, 2000, J. Immunol vol. 164 page 4991-4995) and isolated by cell sorting.

Example 2: Creation of a Bioassay for the Identification of Cells Expressing a Ligand for TREM-1

A TREM-1 reporter cell line was generated by transfecting the NFAT-lacZ bearing cell line BWZ.36 (Sanderson S, Int. Immun. 1994) with hTREM-1 and DAP12 as described in Example 1. This BWZ.36/hTREM-1:DAP12:NFAT-LacZ cell line (herein also referred to as a BWZ/hTREM-1 reporter cell) is highly responsive to antibody-mediated cross linking of TREM-1, giving ˜40-fold induction of the NFAT-driven LacZ production when stimulated with 1-10 μg/ml plate bound commercially available anti-TREM-1 antibody, as compared to the isotype control. NFAT-driven LacZ production in the reporter cells may be assayed using a luminescence based kit, Beta Glow™ (Promega E4720, Madison, Wis.). Plates were coated with isotype control or aTREM-1 MAB1278 (Conc 3 ug/ml in PBS, 100 ul/well) (R&D Systems, Minneapolis, USA) at 4C for 16 hours or for 2 hr at 37° C., 5% CO2 and the BWZ/hTREM-1 reporter cells were detached by adding 10 ml Versene (catalog number #15040, Gibco, Carlsbad Calif., USA), spun at 400 g for 5 min and washed in PBS and media (RPMI-1640 w/o phenol red; cat. number 11835, Gibco, Carlsbad Calif., USA) before adding to the coated plates (1×10⁶ cells/ml, 4×10⁴ cells/well) to total volume 100 ul and incubated overnight (16-20 hours) at 37° C., 5% CO₂.

These TREM-1 responsive cells were used to identify cells expressing TREM-1 ligand. One such cell turned out to be neutrophils from the whole blood. The neutrophils of healthy donors were purified by means of Ficoll and dextran sedimentation and stimulated with PGN (InVivogen, tlrl-pgnsa, SanDiego, Calif., USA) overnight. Briefly, the BWZ/hTREM-1 reporter cells were added to the activated neutrophil cultures in a 1:3 ratio of reporter cell:neutrophils. The assay was run in Poly-D-Lysine coated Black cell culture plates (#356640 from BD Biosciences, San Jose, Calif., USA). TREM-1 activation was read out after 24 hours of culture using the BetaGlo reagent (E4720 from Promega, Madison, Wis., USA) and luminescence measured using a TopCount Luminescence counter from Perkin Elmer.

The vitro stimulated neutrophils possessed a ligand that was able to induce TREM-1 signalling, and neutrophils from the whole blood of healthy donors were purified by Dextran sedimentation and stimulated overnight with multiple reagents. The only reagent that was able to stimulate a TREM-1 responsive signal from neutrophils was PGN-SA (Invivogen, tlrl-pgnsa, SanDiego, Calif., USA) which mimic bacterial activation of the cells. These activated neutrophils were then used to stimulate the BWZ/hTREM-1 reporter cell line, by co-culturing the cells. Briefly, the BWZ/hTREM-1 reporter cells were added to the activated neutrophil cultures in a 1:3 ratio of reporter cell:neutrophils. The assay was run in Poly-D-Lysine coated black cell culture plates (cat. no. 356640 BD Biosciences, San Jose, Calif., USA). TREM-1 activation was read out after 24 hours of culture using the BetaGlo reagent (cat. no. E4720, Promega, Madison, Wis., USA) and luminescence measured using a TopCount Luminescence counter from (Perkin Elmer, Waltham Mass., USA). As shown in FIG. 1, significant induction of reporter activity was observed in BWZ/hTREM-1 cells co-cultured with the PGN-stimulated neutrophils. This induction was highly dependent on neutrophil activation. No response was seen with resting neutrophils (bar 2 neutrophils). Likewise, no response was seen when stimulating BWZ/hTREM-1 reporter cells with PGN-SA in the TLRL cocktail in the absence of neutrophils (bar 1-TLRL), demonstrating that the response is not merely a direct effect of PGN on the BWZ/hTREM-1 cells. Activating neutrophils with cytokine cocktails (bar 3+4 neutrophils+cytokines) did not provide the correct TREM-1 activation signal either.

Example 3: Binding of Soluble TREM-1 to PGN-Activated Neutrophils

PGN-stimulated neutrophils were able to induce TREM-1 activation, indicating the presence of a TREM-1 stimulating factor in the PGN-stimulated neutrophil cultures. In order to confirm the presence of a TREM-1-interacting protein on the neutrophils, PGN-stimulated neutrophils were stained with a recombinant TREM-1-tetrameric protein and analysed by flow cytometry. Briefly, granulocytes were isolated from human whole blood obtained from Astarte Biologics (Redmond, Wash., USA) via a Ficoll-dextran sedimentation method. Blood was stratified on FicollPaque (17-0840-03, GE Healthcare, Piscataway, N.J., USA) gradient with a ratio of 3 parts of Ficoll and 4 parts of blood in a 50 ml tube, then centrifuged at 400×g for 30 minutes at 22° C., without brake. The intermediate PBMC band was gently removed by aspiration. The granulocytes stratified on the packed RBC were aspirated and transferred to a 50 ml polypropylene tube. The granulocytes and contaminating RBCs were diluted to 40 ml with 1× PBS and followed by addition of 10 ml 4% DEXTRAN 500 (Sigma, 31392, St Louis, Mo., USA) in PBS solution. After mixing by gentle inversion, the tubes were left at 22° C. for 20-30 min. A granulocyte rich supernatant was then transferred into a fresh tube and centrifuged at 250×g, 5 min, 22° C.; the supernatant was aspirated and discarded. Contaminating RBCs were removed with an osmotic lysis, briefly, the cell pellet was resuspended in 7.5 ml of 0.2% NaCl; gently mixed for 55-60 seconds and 17.5 ml of a 1.2% NaCl. solution was added. The volume was then brought to 50 ml with PBS and spun at 250×g for 5 min, the pellet was resuspended in 7.5 ml of 0.2% NaCl to repeat the lysis a second time. The final granulocyte pellet was resuspended in RPMI/10% FBS.

Isolated granulocytes were cultured at a density of 3.8 E6/ml in RPMI/10% FBS+10 μg/ml of PGN-SA (Invivogentlrl-pgnsa, San Diego, Calif., USA) for 7 days. Cells were pelleted by centrifugation and resuspended in PBS/2% FBS for staining. Resuspended granulocytes were then plated in a 96 well plate (round bottom) at a density of 100,000/well in the presence or absence of 2 μg/ml of probe, with or without 100 μg/ml (50×) of a specific or irrelevant competitor protein. Cells were incubated with probe/competitor for 1 hour at 4 C in a volume of 50 μl/well. At the end of the incubation, 150 μl/well of PBS/2% FBS was added and the cells were pelleted. The pelleted cells were resuspended in 50 μl/well of goat anti hFc F(ab′)2/PE conjugate (Jackson ImmunoResearch 109-116-098, West Grove, Pa., USA) and incubated at 4° C. for 30 minutes. 150 μl/well of PBS/2% FBS was added and the cells pelleted. Pelleted cells were further washed in 200 ul/well PBS/2% FBS and pelleted. Washed cells were then resuspended in 100 μl/well of fixative (1:1 PBS: Cytofix. 554655, BD Biosciences, San Jose, Calif., USA) and incubated 5 minutes at room temperature. 100 μl/well of PBS/2% FBS was added to fixed cells, then the cells were pelleted. The stained/fixed cells were then resuspended in 100 μl/well of PBS/2% FBS for flow cytometric analysis on a LSR 11 flow cytometer. (BD Biosciences, San Jose, Calif., USA).

Probe Set: Fc mut 5.36 mg/ml SEQ ID NO: 3 hTREM-1 tet/Fc mut 1.07 mg/ml SEQ ID NO: 2 Competitors for hTREM-1 tet/Fc mut: 50X DCIR COMP  0.3 mg/ml SEQ ID NO: 4 50X TREM COMP 1.14 mg/ml SEQ ID NO: 5

Histograms were created from the flow cytometric data. The background fluorescence from the goat anti hFc/PE conjugate was shown in each histogram as the background and was designated “PE”. An identical marker was drawn on each histogram to designate the percentage of cells that bound to the secondary goat anti hFc/PE conjugated antibody. The negative control Fc mut protein showed 2% positive binding cells, which was identical to the background fluorescence seen with the goat anti hFc/PE conjugate alone (FIG. 2A). When cells were stained with 2 μg/ml hTREM-1/tetramer they were 39% positive (FIG. 2B). When the TREM-1 tetramer binding was done in the context of 100 μg/ml DCIR COMP protein, the cells were 41% positive confirming that the DCIR COMP did not compete for binding with TREM-1 tetramer (FIG. 2C). When the TREM-1 tetramer binding was done in the presence of 100 μg/ml of TREM-1 COMP, the cells were 10% positive showing that the TREM COMP protein did compete with TREM-1 tetramer for binding to the cells (FIG. 2D).

Example 4: Identification of PGLYRP1 as a Neutrophil-Expressed TREM-1 Ligand

PGLYRP1 was identified as a TREM-1 ligand through the use of immunoprecipitation coupled with mass spectroscopy (IP-MS). Soluble TREM-1 tetramer was used as an affinity “bait” molecule to identify a ligand. Briefly, TREM-1-tetramer-Fc (SEQ ID NO: 2) and separately CD83-Fc (SEQ ID NO: 5) were each incubated at final concentrations of 100 μg/ml with 270 million human neutrophils, purified by dextran sedimentation as described above, in 1 mL PBS at 4° C., 90 minutes with mild shaking. After pelleting, the cells were resuspended in 1 mL PBS buffer with the inclusion of the crosslinker 3,3′-Dithiobis[sulfosuccinimidylpropionate] (DTSSP) (Thermo Scientific: 21578, Rockford, Ill., USA), at a concentration of 2 mM and incubated 30 minutes at room temperature. Cells were washed 3× with 1 mL PBS followed by lysis in 1 mL RIPA buffer (Thermo Scientific, 89901, Rockford, Ill., USA). The lysate was centrifuged at 15,000×g for 10 minutes at 4° C. to remove insoluble materials. Neutrophil proteins cross-linked to Fc coupled probes were immunoprecipitated from the supernatant using Protein A Mag Sepharose™ beads (GE Healthcare Life Sciences, 28-9670-56, Piscataway, N.J., USA). Briefly, 50 μL of beads were first washed with 200 μL PBS, then resuspended in 1 mL of cell lysate, incubated 60 minutes at 4° C., magnetically captured, and sequentially washed 2× with 200 μl RIPA buffer then 3× with 200 μL PBS. Upon removing PBS from the final magnetic capture, proteins were eluted from the magnetic beads using 200 μL buffer containing 8 M Urea, 100 mM Tris (pH 8.0), and 15 mM TCEP (Thermo Scientific, 77720, Rockford, Ill., USA) and incubated at room temperature for 30 minutes, beads were captured and supernatant was transferred to a Microcon Ultracel YM-30 filter (Millipore, 42410, Billerica, Mass., USA). Samples were spun at 14,000×g, 20° C., 30-60 minutes until no liquid remained on the top of the filter membrane. The retained proteins were then alkylated with 100 μL 50 mM IAA (iodoacetamide) in 8 M Urea for 30 minutes in dark at room temperature. The filter was washed 2× with 100 μL 50 mM NH₄HCO₃ and then transferred to a new collection tube. 1 μg trypsin (cat. no. V5111, Promega, Madison Wis., USA) in 60 μL 50 mM NH₄HCO₃ was added followed by incubation at 37° C. overnight. The tryptic digest was collected by centrifugation at 14,000×g for 30 minutes followed by washing the filter with 50 μL 50 mM NH₄HCO₃. 10 μL of the digest was analyzed by LC/MS/MS using an LTQ-Orbitrap-XL mass spectrometer (Thermo Scientific, Waltham, Mass., USA). The data was searched against IPI human database (v3.81) using SEQUEST-Sorcerer engine (4.0.4 build) (SageN, Milpitas, Calif., USA) and then post processed with Scaffold 3 (Proteome Software, Portland, Oreg., USA) to filter protein IDs with a false discovery rate of 1%. After negative control subtraction, PGLYRP1 was found to be a high-confidence protein specifically associated with hTREM-1 tetramer. The immunoprecipitation in the neutrophils showed that out of the 148 identified proteins, 72 proteins were immunoprecipitated by the control construct (CD83) alone, 73 of the proteins were identical for TREM-1 and CD83, whereas only three were TREM-1 specific (FIG. 3A and FIG. 3B). The experiment was subsequently repeated using neutrophils from a different donor and PGLYRP1 was again identified as specifically interacting with hTREM-1.

Example 5: Purification of Human PGLYRP1 Expressed from HEK293 6E

A recombinant protein sequence was constructed by fusing the human CD33 signal peptide sequence (SEQ ID NO: 53) with the human mature PGLYRP1 coding sequence (SEQ ID NO: 1). The resulting open reading frame was cloned into pcDNA3.1/Zeo(+) vector (Life Technologies, Carlsbad Calif., USA) after a CMV promoter. The pcDNA3.1-hPGLYRP1 construct was then transfected into HEK293 6E cells with 293Fectin™ (Life Technologies, Carlsbad Calif., USA) following the vendor's protocol. 5 days after transfection, the culture supernatant containing secreted human PGLYRP1 was harvested by centrifugation (15,000 rpm×20 min, 4 □C) and then cleared by the filtration with 0.22 μm cellulose nitrate membrane. The cleared supernatant was first diluted 10 fold into 20 mM sodium citrate pH 5.0 and then applied to a Hitrap SP HP 5 ml column (17-1151-01 GE Healthcare, Uppsala, Sweden), followed by a 5 column volume wash with 20 mM sodium citrate pH5.0. The bound human PGLYRP1 was then eluted with a 0-100% linear gradient of 20 mM sodium citrate pH 5.0, 1M NaCl in 30 column volumes. The fractions containing dimer and monomer forms of human PGLYRP1 were pooled separately and concentrated to less than 4 ml by Amicon ultra 15 centrifugal units (UFC800324 3,000 kDa MWCO, Millipore, Hellerup, Denmark). Dimer and monomer pools were further polished and buffer-exchanged to Phosphate Buffered Saline (PBS) by a Hiload 26/60 Superdex 75 318 ml column (17-1070-01 GE Healthcare, Uppsala, Sweden). After concentrating, the final protein concentrations were determined by measuring 280 nm absorbance with a NANODROP UV spectrometer. Protein purity was assessed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE).

Example 6: Refolding and Purification of Human PGLYRP1 Expressed from E. Coli

Human PGLYRP1 was expressed as inclusion bodies in Escherichia coli BL21 (DE3) cells. Bacteria were harvested by centrifugation, resuspended in 50 mM Tris-HCl pH8.0, 500 mM NaCl, 5 mM EDTA, 0.5% Triton X-100 and disrupted by sonication. The insoluble pellet was washed three times with 50 mM Tris, pH 8.0, 1% TritonX-100, 2 M urea and once with 50 mM Tris pH 8.0, then solubilized in 50 mM Tris-HCl, 6M guanidine hydrochloride, pH7.4, 1 mM DTT (final protein concentration 20 mg/ml). For in vitro folding, solubilized human PGLYRP1 inclusion bodies were diluted into 50 mM Tris, pH 8.0, 2 mM EDTA, 5 mM cysteamine, 0.5 mM cystamine, 0.4 M arginine (final protein concentration 1 mg/ml). After overnight at 4° C., the folding mixture was cleared by centrifugation/filtration and then diluted 12 fold into 10 mM MES pH 3.5 to lower the conductivity and pH (final pH ˜5.8, conductivity ˜6 mS/cm). The diluted folding mixture was then applied to a Hitrap SP HP 5 ml column (17-1151-01 GE Healthcare, Uppsala, Sweden), followed by a 5 column volume wash with 50 mM MES pH 5.8. The bound human PGLYRP1 was then eluted with a 0˜60% linear gradient of 50 mM MES pH 5.8, 1 M NaCl in 20 column volume. The fractions containing refolded human PGLYRP1 were pooled and concentrated to less than 4 ml by Amicon ultra 15 centrifugal units (UFC800324 3,000 kDa MWCO, Millipore, Hellerup, Denmark). A Hiload 26/60 Superdex 75 318 ml column ((17-1070-01 GE Healthcare, Uppsala, Sweden) was then used to polish and buffer-exchange the proteins to Phosphate Buffered Saline (PBS). Majority of refolded human PGLYRP1 proteins was in monomer form. After concentrating, the final protein concentration was determined by measuring 280 nm absorbance with a NANODROP UV spectrometer. Protein purity was assessed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE).

Example 7: Immunisation of Mice and Identification of mAbs

Purified human PGLYRP1 was used to immunize mice in order to raise antibodies. Briefly, mice were immunised 3 times with 20 μg recombinant PGLYRP1 per immunisation. The first immunisation was subcutaneous using Complete Freunds Adjuvant (cat. no. 3018, Statens Serum Institut, Copenhagen, Denmark). The following two immunisations were intraperitoneal using Incomplete Freunds Adjuvant (cat. no. 3016, Statens Serum Institut, Copenhagen, Denmark). Ten days after the last immunisation, cheek blood was drawn and the sera were tested against PGLYRP1 in a direct ELISA.

Example 8: Binding of Soluble TREM-1 to PGLYRP1

One common method of validating a novel protein-protein interaction is through reconstituting the interaction using recombinant reagents. To this end recombinant human PGLYRP1 was expressed with a C-terminal epitope signalling the posttranslational addition of a glycosylphosphatidylinositol (GPI) structure. Proteins containing terminal GPI structures are targeted for display on the plasma membrane. This commonly applied technique allows otherwise soluble proteins to be displayed and tested for binding by flow cytometric techniques. In FIG. 4A, HEK-2936E cells were transfected with pCDNA 3.1/zeo(+) hPGLYRP1-GPI (SEQ ID NO: 7) 3 μg of DNA was diluted into 100 μl of Optimem (Cat. no. 31985062, Life Technologies, Carlsbad, Calif., USA). 4 μl of 293fectin (Cat. no. 51-0031, Life Technologies, Carlsbad, Calif., USA) was added to 100 μl of Optimem (Cat. no. 31985062, Life Technologies, Carlsbad, Calif., USA) and incubated at 22° C. for 5 minutes. The DNA/Optimem mix and the 293fectin/Optimem mix were combined and incubated for an additional 20 minutes at room temperature. HEK-2936E cells were diluted to 3 mls at 1 e6/ml in Freestyle media (Cat. no. 12338, Life Technologies, Carlsbad, Calif., USA) and plated in a 6-well dish (Cat. no. 35-3046, Biosciences San Jose, Calif., USA) and then the DNA/293fectin mix was added dropwise to the cells. Cells were incubated for 48 hours at 37° C. with shaking. 1 μg/ml of human TREM-1-G4Sx3-TREM-1/Fc6mut (SEQ ID NO: 2) was diluted in PBS/2% FBS and 50 μl of probe was added to 80,000 transfected HEK293-6E cells in a round bottom 96-well plate (Cat. no. 3799, Costar, Lowell, Mass., USA). Cells were incubated at 4° C. for 1 hr followed by 2× washes with 200 μl PBS/2% FBS. 50 μl of 1 μg/ml PE goat anti-human Fc (Cat. no. 109-116-098, Jackson ImmunoResearch, West Grove, Pa., USA) was added and incubated for an additional hour followed by 2×PBS/2% FBS washes. Cells were fixed for 5 min in 1:1 PBS diluted BDCytofix (Cat. no. 554655, BD Biosciences, San Jose, Calif., USA) and incubated for 5 mins followed by a 200 μl PBS/2% FBS wash. Cells were resuspended in 100 μl PBS/2% FBS before being analyzed on a FACS LSRII (BD Biosciences, San Jose, Calif.). The results of this experiment are shown in FIG. 4A where unstained cells are shown by solid black line (G03). TREM-1-G4Sx3-TREM-1/Fc6mut staining of mock transfected cells is shown dashed line, and shows no binding relative to unstained cells. Finally, cells transfected with human PGLYRP1-GPI robustly bind TREM-1-G4Sx3-TREM-1/Fc6mut shown with the dotted line. Quantitation of binding is expressed as mean florescent intensity, MFI.

In addition to flow cytometry, protein-protein interactions are also commonly assessed by measuring surface plasmon resonance (SPR). A BiacoreT200 (GE Healthcare, Piscataway, N.J., USA) instrument was used to analyze the interaction between human TREM-1 & human PGLYRP1 and also between human PGLYRP1 & sonicated, soluble E. coli peptidoglycan (Cat. no. tlrl-ksspgn, Invivogen, San Diego, Calif., USA). All assays were performed at 25° C. at flow rates of 20-30 μL/minute in 1×HBS-P running buffer (Cat. no. BR-1006-71, GE Healthcare, Piscataway, N.J., USA).

In FIG. 4B, 4641.1 RU of human TREM-1 tetramer (SEQ ID NO: 2) was amine coupled to a Biacore CM5 chip (Cat. no. BR-1005-30, BR-1000-50, GE Healthcare, Piscataway, N.J., USA) following the manufacturer's recommended methods. PGLYRP1 (Cat. no. 2590-PG, R&D Systems, Minneapolis, USA) was diluted to 150 nM in 1×HBS-P running buffer (Cat. no. BR-1006-71, GE Healthcare, Piscataway, N.J., USA) in the presence or absence of 10 μg/mL soluble E. coli peptidoglycan (Cat. no. tlrl-ksspgn, Invivogen, San Diego, Calif., USA) and injected over the TREM-1 surface. Data is reference subtracted vs. an activated and blocked (with ethanolamine) reference surface. Though PGLYRP1 binds TREM-1 both in presence and absence of PGN, there appears to be a significant avidity effect when PGLYRP1 is crosslinked by PGN.

In FIG. 4C, 274.8 RU of PGLYRP1 dimer (SEQ ID NO: 1) were amine coupled to a Biacore CM5 chip (Cat. no. BR-1005-30, BR-1000-50, GE Healthcare, Piscataway, N.J.). Soluble E. coli peptidoglycan (Cat. no. tlrl-ksspgn, Invivogen, San Diego, Calif., USA) was diluted to 10 μg/mL in 1×HBS-P running buffer (Cat. no. BR-1006-71, GE Healthcare, Piscataway, N.J., USA) and injected over the PGLYRP1 surface. Data is reference subtracted vs. an activated and blocked (with ethanolamine) reference surface.

In FIG. 4D, the same chip was used as in FIG. 4C, (274.8 RU of PGLYRP1 dimer, (SEQ ID NO: 1). TREM-1 dimer (SEQ ID NO: 8) was diluted to 150 nM in 1×HBS-P running buffer (BR-1006-71, GE Healthcare, Piscataway, N.J., USA) and injected both before and after repeated injections of peptidoglycan (depicted in FIG. B). Data is reference subtracted vs. an activated and blocked (with ethanolamine) reference surface and the signal of a buffer blank injection is also subtracted. TREM-1 shows clear binding to immobilized PGLYRP1. Soluble TREM-1 dimer binds similarly to immobilized PGLYRP1 alone or to PGLYRP1 that has been loaded with PGN. Overall binding of surface immobilized TREM-1 receptor by soluble PGLYRP1 and PGN consists of a modest affinity for the PGLYRP1:TREM-1 complex enhanced by an avidity effect from the highly crosslinked PGLYRP1.

Example 9: Activation of TREM-1-Response by Recombinant PGLYRP1

To test if recombinant PGLYRP1 can activate a TREM-1 response, the BWZ/hTREM-1 reporter cell line was seeded into black 96 well plates and stimulated with recombinant human PGLYRP1 (Cat. no. 2590-PG-050, R&D Systems: Minneapolis, Minn.) in the presence or absence of 10 μg/ml PGN. TREM-1 activation was read out after 24 hours of culture using the BetaGlo reagent (Cat. no. E4720, Promega Madison, Wis., USA) and luminescence measured using a TopCount Luminescence counter from Perkin Elmer. As shown in FIG. 5A, stimulation of the TREM-1 reporter cell line with PGLYRP1 induced a dose-dependent activation of TREM-1 in the presence of PGN. Several different PGN were tested, including PGN-EC (from E. coli), PGN-SA (from S. aureus) and PGN-BS (from B. subtilis) (Invivogen, San Diego, Calif., USA), and were all able to fascilitate the PGLYRP1-induced TREM-1 response.

The response induced by recombinant PGLYRP1 could be inhibited by addition of a recombinant TREM-1-Fc-fusion protein (SEQ ID NO: 2) (FIG. 5B) or by addition of polyclonal anti-PGLYRP1 antibody (Cat. no. AF-2590, R&D Systems: Minneapolis, Minn., USA) confirming that PGLYRP1 is the TREM-1 ligand and that soluble TREM-1 and anti-PGLYRP1 are potentially useful as TREM-1 antagonists.

Example 10: TNFalpha Release from M1 Macrophages Stimulated by PGLYRP1

Monocytes were differentiated into M1 macrophages and stimulated with PGLYRP1 complex resulting in TNFalpha release in two different donors.

Those skilled in the art will recognize the value of establishing a freezer bank collection of primary cells from multiple donors thus providing for convenient replication of experiments. In vitro derived macrophages were produced from peripheral blood monocytes as follows. Negatively enriched monocytes were isolated from a peripheral blood “leukopak” obtained from Research Blood Components (Brighton, Mass., USA) using a Rosette Sep kit (cat. no. Cat. no. 15068 Stem Cell Technologies, Vancouver BC, Canada) following the manufacturer's instructions. Isolated monocytes were suspended in 10% DMSO/FBS aliquots of 50 e6 cell/ml and gradually cooled to −80 C. To produce macrophage cells, one or more frozen vials of monocytes were rapidly thawed in a 37 C water bath, diluted to 10 ml with growth media [RPMI 1640 (Cat. no. 72400-047, Life Technologies, Carlsbad Calif., USA)) with 10% FBS (Cat. no. 03-600-511, Themo Fisher, Waltham Mass., USA) and centrifuged 5 minutes at 250 g. Cells were suspended to 2 e6 cells/ml in growth media supplemented with 50 ng/ml human MCSF (Cat. no. PHC9501, Life Technologies, Carlsbad Calif., USA), placed into tissue culture treated, petri style tissue culture plates and into a humidified incubator programmed to maintain a “hypoxic” atmosphere of 5% CO2, 2% O2. On the third day in culture, the cells were fed with the addition of an equal volume of growth media supplemented with 50 ng/ml human MCSF. After 6 days in culture the monocytes had differentiated into MO macrophages. M0 cells were further differentiated by changing the media to growth media supplemented with 50 ng/ml human IFNg (Cat. no., PHC4031, Life Technologies, Carlsbad Calif., USA) for M1 macrophages or 40 ng/ml human IL-4 (Cat. no. PHC0045, Life Technologies, Carlsbad Calif., USA) for M2 macrophages and returning to the incubator for an additional 22 hours. On the seventh day, macrophages were suitably differentiated to be used in a bioassay. Briefly, macrophages were recovered from the petri plates by washing with 1×PBS, followed by 5 mM EDTA in PBS. The plates were then returned to 37 C for 30 minutes and cells were “power washed” off the plate using a 10 ml syringe and 22 G needle. Cells were then diluted into growth media, centrifuged at 250 g for 5 minutes after which the cell pellet was suspended to a final concentration of 1 e6/ml.

Macrophage cells prepared as above were used in bioassays where cytokines such as TNF-alpha produced in response to stimulation of the cells with TREM-1 ligand were measured in the conditioned media by ELISA. Such a bioassay was further utilized to measure blockade of TREM-1 ligand stimulation by TREM-1 specific antibodies. TREM ligand or negative controls were prepared at 4× concentrations in growth media and 50 microliters/well were added to 96 well microtiter dishes. Final concentrations of TREM-1 ligand consisted of 7.5 ng/ml recombinant human PGLYRP1 (generated as described in example 5) and 3 μg/ml PGN-BS (Cat. no., tlrl-pgnbs, Invivogen, SanDiego Calif., USA). Cells were cultured under humidified hypoxic conditions as described above for 22 hours after which conditioned media was collected and TNF-alpha levels were measured by ELISA, following manufacturer's instructions (Cat. no. DY210, R&D Systems, Minneapolis Minn., USA).

Donor 1 Donor 2 TNF-α, TNF-α, pg/ml pg/ml M1 macrophage with: Avg SD Avg SD No addition 0 0 22 1 0.4 μg/ml PGN-BS 357 153 764 139 2.0 μg/ml PGN-BS 3086 151 5792 226 5 μg/ml PGLYRP1 + 0.4 μg/ml 7502 384 7819 945 PGN-BS 5 μg/ml PGLYRP1 + 2 μg/ml PGN-BS 31440 1030 40418 1633 This example shows that the TREM-1 ligand PGLYRP1 is able to further increase TNFa release from macrophages from two different donors.

Example 11: Cytokine Release from Synovial Tissue Cells from RA Patients Upon Stimulation with PGLYRP1

Synovial tissue samples were obtained from RA patients during total knee replacement. Single suspension of synovial tissue cells was isolated by a digestion via 4 mg/ml of collagenase (Cat. no. 11088793001, Roche, Mannheim, Germany) and 0.1 mg/ml of DNase (Cat. no. 11284932001, Roche, Mannheim, Germany) for 1 h at 37 degree. Synovial tissue cells at 1×10^5/well in culture medium RPMI (Cat. no. R0883, Sigma Aldrich, St Louis, Mo., USA) +10% FCS (Cat. no. S0115, BioChrom AG, Grand Island, N.Y. 14072, USA) were stimulated with 4 ug/ml of PGLYRP1 and 1 ug/ml of PGN-ECNDi (Cat. no. tlrl-kipgn, Invivogen,San Diego, Calif. 92121, USA). After 24 h incubation, cell supernatants were harvested, and cytokines were measured by either ELISA (TNFa (Cat. no. DY210, R&D Systems, Minneapolis, Minn. 55413 USA), IL-1b (Cat. no. 88-7010-88, eBioscience, San Diego Calif. USA), GM-CSF (Cat. no. 88-7339-88, eBioscience, San Diego Calif. USA) or Flowcytomix (TNFa, IL-1b, MIP-1b, MCP-1, IL-6, and IL-8 (Cat. no. BMS, eBioscience, San Diego Calif. USA). The cytokines were secreted from the synovial tissue cells upon stimulation with the TREM-1 ligand.

Cytokine (pg/ml) PGN PGN + PGLYRP1 TNFalpha 623.69 1444.59 IL-1beta 2419.42 3772.74 GM-CSF 181.91 615.91 MIP-1beta 2457.955 4394.725 MCP-1 273.055 471.26 IL-6 2056.94 4189.355 IL-8 2574.56 5509.195 This example shows that cells from synovial tissue from rheumatoid arthritis patients will respond to stimulation by the TREM-1 ligand PGLYRP1 by secreting numerous cytokines.

Example 12: Identification of Anti-PGLYRP1 mAbs that Inhibit TREM-1 Activation

In order to identify monoclonal anti-PGLYRP1 mAbs that can block TREM-1 responses, wtbalb/c mice were immunized with recombinant human PGLYRP1. Primary screening was done by means of direct ELISA on PGLYRP1 protein, and all PGLYRP1-specific hybridoma supernatants were subsequently tested in the BWZ/hTREM-1 reporter cell assay to identify monoclonal anti-PGLYRP1 antibodies capable of inhibiting TREM-1 activation induced by PGN-stimulated neutrophils, as described under example 1. The bioassay was run as follows: 40,000 hTREM-1/BWZ.36 cells/well were plated in a clear bottom, black 96 well plate in the presence of 75 ng/ml PGLYRP1 (SEQ ID NO: 1) with 2.5 pg/ml PGN-ECndi (Cat. no. tlrl-kipgn, Invivogen San Diego, Calif., USA) to provide a sub-maximal positive signal, or alternatively in the presence of a sub-maximal level (1 μg/ml) of plastic adsorbed anti TREM-1 monoclonal antibody (Cat. no. MAB1278 R&D Systems, Minneapolis, Minn., USA) to provide a positive signal. Test antibodies were titered into the assay starting at 10 μg/ml, with 5 serial 2-fold dilutions. The assay was incubated overnight at 37 C, and developed with Beta Glo (Cat. no. E4740,Promega Madison, Wis., USA), as per the Beta Glo protocol, and luminescence was recorded. Data was plotted showing Beta Glo relative luminescent units vs test antibody concentration. Non-neutralizing negative control mIgG1 (Cat. no. MAB002, R&D Systems Minneapolis, Minn., USA) and neutralizing positive control polyclonal goat anti hPGLYRP1 antibody (Cat. no. AF2590, R&D Systems, Minneapolis, Minn., USA) were run on each assay plate. As shown in FIG. 6A, F10, F14, F29, F36, F38, F77, F95 and F105 were identified as being able to block the TREM-1 response to PGLYRP1. FIG. 6B shows other PGLYRP1 antibody hybridoma supernatants able to block the TREM-1 dependent signal. M-hPGRPS-2F5 (SEQ ID NOs: 31-32 and -2F7 (SEQ ID NOs: 35-36) are very efficient blockers. In contrast, testing of commercially available monoclonal anti-PGLYRP1 antibodies in the same assay protocol alongside the antiPGLYRP1 goat polyclonal positive control (Cat. no. AF2590, R&D Systems Minneapolis, Minn., USA) showed that none of these could block TREM-1 activation (FIG. 6C). The anti PGLYRP1 antibodies tested include: 188C424 from Thermo Scientific (6D), 4H230 and 9A319 Mabs from US Biological (FIG. 6D, 6E); all failed to block PGLYRP1 stimulation of the TREM-1 bioassay. Clone 6D653 from Santa Cruz Biotechnology (FIGS. 6F and 6G) had was found to block the assay non-specifically based on the observation that the Mab blocked both PGLYRP1 (6F) and anti-TREM-1 stimulation (6G) while the positive control anti PGLYRP1 polyclonal Ab only blocked PGLYRP1 mediated activation. This non-specific blocking may be due to azide toxicity on the bioassay.

In conclusion, PGLYRP1 monoclonal antibodies have been identified that not only bind PGLYRP1 but also neutralize its TREM-1 signalling activity. The method used to identify these molecules provides a unique advantage over routine methods used to identify PGLYRP1 antibodies, evidenced by the failure of available commercial antibodies to neutralize PGLYRP1.

Example 13: PGLYRP1 Antibodies Block a TREM-1 Specific Signal

PGLYRP1 hybridoma clones were sequenced and recombinantly expressed as a hIgG4 antibody. Two of these mAb 0182 (from 1F36) (SEQ ID 15 and 16) and mAb 0184 (from 1F105) (SEQ ID 23 and 24) were retested in the BWZ/hTREM-1 reporter cell assay as described in example 13. These anti-PGLYRP1 antibodies block the TREM-1 response in the BWZ/hTREM-1 reporter cell assay in a dose-dependent manner.

BWZ.36/hTREM-1 response, Beta Glo RLU Antibody Isotype 182 184 ug/ml Avg SD Avg SD Avg SD 0 74636 10004 74636 10004 74636 10004 0.16 70289 13018 81858 3336 60738 5449 0.31 68555 5585 73382 650 59830 2837 0.63 68105 11547 73831 7818 51198 397 1.25 71797 8545 63280 1663 46447 708 2.5 69207 5004 51675 1270 42062 1953 5 76951 901 33641 842 36194 1461 10 83930 8962 20655 1080 25239 407 20 74555 511 11852 464 21333 115 40 72296 8228 7696 306 15693 1861

This example shows that, in contrast to the commercial available antibodies against PGLYRP1 shown in FIG. 6C-G, the PGLYRP1 antibodies disclosed herein are able to block the TREM-1 specific signal in the BWZ/hTREM-1 reporter cell assay.

Example 14: TNF-Alpha Release from M2 Macrophages Stimulated by PGLYRP1

Monocytes were differentiated into M2 macrophages and stimulated with PGLYRP1 complex. Antibodies (10 μg/ml) mAb-0182 and -0184 directed against PGLYRP1 is able to lower the TNF-alpha release. M2 macrophages were differentiated as described in Example 10. Antibodies to be tested were prepared at 4× concentrations in growth media and 50 microliters/well were added. The final step in initiating the bioassay was the addition of 100 microliters/well of M2 macrophage cells prepared as described above. PGLYRP1 monoclonal antibodies (mAb 0182 and mAb 0184) were tested for neutralizing activity on M2 macrophages. Duplicate (unless otherwise noted) test wells were tested under the following conditions: no added stimulation, 7.5 ng/ml PGLYRP1 only, 3 μg/ml PGN-BS (Cat. no. tlrl-pgnbs, Invivogen San Diego, Calif., USA) only (sextuplicates), PGLYRP1 with PGN-BS (sextuplicates), and PGLYRP1 with PGN-BS in the presence of PGLYRP1 antibodies or hIgG4 isotype control antibody titrated in at concentrations between 40 μg/ml and 0.31 μg/ml in 2 fold dilutions.

Donor 1 Donor 2 TNF-α, TNF-α, pg/ml pg/ml M2 macrophages with: Avg SD Avg SD No addition 108 42 68 16 PGLYRP1 167 98 89 33 PGN 424 105 635 156 PGLYRP1 + PGN 1660 198 2168 210 PGLYRP1 + PGN + isotype 1726 182 2483 251 PGLYRP1 + PGN + mAb 0182 1322 173 2014 107 PGLYRP1 + PGN + mAb 0184 1207 168 1948 173

This example illustrates that the TREM-1 ligand PGLYRP1 is able to further increase TNFa release from M2 macrophages from two different donors and that the antibodies disclosed herein are able to decrease such TNFa release. Therefore, these PGLYRP1 antibodies are potentially useful as TREM-1 antagonists.

Example 15: Survey of Binding Interactions Between TREM-1 and PGLYRP1 Related Molecules Confirms Specificity

Having identified TREM-1 as being able to bind to PGLYRP1 and activate TREM-1 in the presence of PGN, we set out to determine whether or not TREM-1 could bind to the other PGLYRP family members. PGLYRP1 was artifically anchored in the cell-membrane through addition, at the N-terminus, of an intracellular (IC) and transmembrane domain (TM) derived from the Type II receptor MDL-1. The latter constructs were denoted Type II PGLYRP1. In Type II 1.0 (SEQ ID NO: 37), the charged amino acid of the native MDL-1 receptor TM is maintained, and efficient expression of this protein, is dependent on co-expression of DAP12. In the Type II 2.0 PGLYRP1 construct (SEQ ID NO: 38), the charged TM residue has been substituted with a neutral amino acid (Lysine to Leucine), enabling the protein to be expressed independently of eg. DAP12, and an epitope tag of DYKDDDDK (SEQ ID NO: 39) was added. Full length hPGLYRP2 (SEQ ID NO: 40), hPGLYRP3 (SEQ ID NO: 41), and hPGLYRP4 (SEQ ID NO: 42]), cDNAs were synthesised as membrane anchored proteins using N terminal fusion of the Type II 2.0 MDL1 N terminus as utilized for PGLYRP1 above. cDNAs were subcloned into a modified pTT5 expression plasmid vector (Zhang J et al. Protein Expression and Purification, Vol. 65, Issue 1, May 2009, pp 77-8), and transfected as described in example 8 into HEK293-6E cells alongside an empty vector negative control (Mock). Cells were assayed by flow cytometry for both surface and intracellular binding of the following probes: goat anti-human PGLYRP1 (PGRPS) (Cat. no. AF2590, R&D Systems, Minneapolis, Minn., USA); Mab anti-human PGLYRP2 (PGRP-L) (Cat. no. MAB0755, Abnova, Walnut, Calif., USA); Mab anti-human PGLYRP3 (PGRP-1a) (Cat. no. MAB0068, Abnova, Walnut, Calif., USA); Mab anti-human PGLYRP3 (PGRP-1a) (Cat. no. ab13901, Abcam, Cambridge Mass., USA); rabbit anti-human PGLYRP3 (PGRP-1a) (Cat. no. 18082-1-AP, Protein Tech, Chicago Ill., USA); goat anti-human PGLYRP4-biotin (PGRP-1b) (Cat. no. BAF3018, R&D Systems, Minneapolis, Minn., USA); goat anti-mouse PGLYRP1 (PGRPS) (Cat. no. AF2696, R&D Systems, Minneapolis, Minn., USA); huTREM-1.Fc dimer (C0099); huTREML1.Fc dimer (CO246); huTREML2.Fc dimer (CO247); huTREM2.Fc dimer (CO248); The binding protocol was conducted as follows, using either cytofix/perm buffer (Cat. no. 51.2090KZ, BD Biosciences, San Jose Calif., USA) for intracellular staining or 2% FBS/PBS for surface staining: cell pellets were resuspended in a 96-well round bottom plate (to begin with: 160,000 cells/well) with 200 μl cytofix/perm buffer for 15 minutes at 22 C, washed twice with 200 μl 1× PermWash Buffer (diluted 10× in DiH20), stained with 50 μl probe diluted to 5 □g/ml in 1× PermWash buffer, incubated for 1 hour at 4 C, cells were then washed with 200 μl 1× PermWash Buffer, a secondary probe was added in 50 μl 1× PermWash buffer, cells were incubated at 4 C for 30 minutes, washed twice with 200 μl 1× PermWash Buffer, pellets were resuspended in 50 μl 1:1 PBS diluted CytoFix (BD:554655, San Jose, Calif.), incubated for 5 minutes at 22 C, 150 μl PBS/2% FBS was added, centrifuged for 5 minutes at 300 g, washed 1× with 200 μl PBS/2% FB Sand resuspended in 100 ∞l PBS/2% FBS. Binding was analysed using FACS on LSRII (BD, San Jose Calif., USA).

As summarised in the table below, TREM-1 probe bound exclusively to hPGLYRP1 and no hTREM family member binding to PGLYRP2, PGLYRP3 or PGLYRP4 was detected.

Type II Type II Type II Type II Type II Type II Mock PGLYRP1 PGLYRP2 PGLYRP3 PGLYRP4 PGLYRP3 + 4 muPGLYRP1 anti − ++++ − − ++ + ++++ huPGLYRP1 (R&D, AF2590) anti − − ++++ − − − n/d huPGLYRP2 (Abnova, MAB07755) anti − − − − − − n/d huPGLYRP3 (Abnova, MAB0068) anti − − − − − − n/d huPGLYRP3 (Abcam, ab13901) anti − − − − − − n/d huPGLYRP3 (Proteintech, 18082-1-AP) anti − ++++ − − ++++ ++++ n/d huPGLYRP4 (R&D, BAF3018) anti − ++++ n/d n/d n/d n/d ++++ muPGLYRP1 (R&D, AF2696) huTrem1.Fc − ++++ − − − − − (C0099) huTremL1.Fc − − − − − − − (C0246) huTremL2.Fc − − − − − − n/d (C0247) huTrem2.Fc − − − − − − n/d (C0248)

Human membrane anchored PGLYRP1, PGLYRP2, PGLYRP3 and PGLYRP4 were transiently expressed in HEK293 and probed with both in-house and commercial soluble receptors and antibodies in order to identify new interactions between family members. Binding scores were expressed as “n/d”, “−”, “+” or “++++”. Scores are a ratio of mean florescent intensity (MFI) of probe staining over negative control staining; “−” equals a ratio of <1, “++++” represents a score of >30 and “++” represents approximately 10-15, “+” represents 2-5 with a statistically significant difference (p<0.05). Those skilled in the art may characterize this scoring as negative, bright or dim respectively.

TREM-1 only binds to PGLYRP1 and none of the other PGLYRP members, and vice versa: PGLYRP1 only interacts with TREM-1 and none of the other TREM members.

Example 16: TREM-1 Ligand is Present in RA Synovial Fluid Samples

Rheumatoid arthritis is characterized by metacarpophalageal (MCP) joint inflammation in which activated granulocytes play a significant role. PGYLRP1 was assayed by ELISA and tested in BWZ/hTREM-1 reporter cell assay from synovial fluid drawn from MCP joints of 9 RA patients. Commercially sourced synovial fluid (Asterand, Detroit Mich., USA) was thawed, vortexed and serially diluted in ELISA buffer and run in a PGLYRP1 assay following the manufacturers guidelines (Promega, Madison Wis., USA) Four of 9 patients showed elevated PGLYRP1 levels:

PGLYRP1, ng/ml RA SF donor Avg SD 1 14 5 2 8 1 3 213 44 4 229 58 5 135 49 6 47 4 7 39 13 8 116 33 9 32 1

The RA synovial fluid samples were subsequently assayed for TREM ligand activity in the BWZ reporter assay as described in example 2. Briefly synovial fluid was thawed, vortexed, and serially diluted, assayed in duplicate +/−10 μg/ml PGNECndi (Invivogen, SanDiego, Calif., USA) with the addition of polyclonal PGLYRP1 antibody (Cat. no. AF2590, Promega, Madison Wis., USA) or a negative control polyclonal. Plastic adhered monoclonal TREM-1 and isotype antibodies (R&D Systems, Minneaopolis Minn., USA) served as positive and negative controls respectively. FIG. 8 illustrates an example of how the synovial fluid from a rheumatoid arthritis patient is able to trigger the BWZ/hTREM-1 reporter cell assay in a PGLYRP1 dependent manner.

Example 17: Assembly of Mammalian Expression Vectors Useful in the Identification and Characterization of the PGLYRP1: TREM 1 Interaction

A.) Construction of pJSV002 hTREM-1-G4Sx3-hTREM-1/Fc6mut (SEQ ID NO: 9)

An Fc receptor binding deficient version of human IgG1 was built by eliminating the first 215 amino acids of human IgG1 comprising the variable and constant one (CH1) domain and making the following amino acid substitutions within the hinge, constant 2 and constant 3 domains: (E216G, C220S, L234A, L235E, G237A, A330S, P331S). This construct was given the name Fc6mut since six mutations were made to modulate binding to Fc receptors while a 7^(th) mutation (E216G) was incorporated to create a ApaI restriction cloning site. These mutations were built into pJSV002 (modified pTT5, Zhang J et al. Protein Expression and Purification, Vol. 65, Issue 1, May 2009, pp 77-8) allow cloning of extracellular domains of receptors 5′ of Fc6mut as EcoRI/ApaI fragments. A cDNA was synthesised with a 5′ EcoRI restriction site, a GCCACC Kozak sequence the CD33 leader sequence followed by the extracellular domain of human TREM-1 (aa17-200) with a interspaced KpnI restriction site and glycine-glycine-glycine-serine spacer repeated three times (G4Sx3) followed by an additional copy of the extracellular domain of human TREM-1 (aa17-200) and an Apa1 site to allow cloning upstream of the Fc6mut. This synthesised DNA was cut with EcoRI and ApaI and ligated into pJSV002 Fc6mut that had also been prepared with an EcoRI/ApaI digestion. This ligation was electroporated into DH10B E. coli and plated onto ampicillin agar plates. Individual clones were grown overnight in 2 mls LB+ampicillin cultures and miniprepped followed by restriction screening with EcoRI/ApaI to find clones with the appropriate 1219 base pair insert. Correct clones were sequenced, and one of the correct clones (#519) was selected for preparation of additional DNA by big prep.

B.) Construction of hTREM-1-COMP-SBP38x2-6His (SEQ ID NO: 10)

To create a pentameric TREM ECD molecule, a C terminal epitope tag was created in the pJSV002 expression vector. A synthetic cDNA encoding the 3′ end of cartilage oligomeric protein (COMP) was fused to two copies of the streptavidin binding protein domain (SBP) followed by a C-terminal 6× His domain, built into pJSV002 such that extracellular domains of receptors could be cloned 5′ as of this fragment, as an EcoRI/KpnI fragment. Subsequently a hTREMcDNA was synthesised containing an EcoRI restriction site followed by GCCACC Kozak sequence and the extracellular domain of human TREM-1 with a C-terminal KpnI site. This EcoRI/KpnI fragment was ligated into pJSV002 COMP-SBP38x2-6His vector described above. This ligation was electroporated into DH10B E. coli (Life Technolohies, Carlsbad Calif., USA) and plated onto ampicillin agar plates. Individual clones were grown overnight in 2 mls LB+ampicillin cultures and miniprepped followed by restriction screening with EcoRI/KpnI to find clones with the appropriate 616 bp insert. Correct clones were sequenced, and one of the correct clones #525 was selected for preparation of additional DNA by big prep. The full length cDNA is listed as SEQ ID NO: 10.

C.) Construction of pJSV002 hCD83-G4Sx3-hCD83/Fc6mut (SEQ ID NO: 11)

hCD83 tetramer has previously been shown to have low binding by FACS analysis when tested against a wide range of cell lines and therefore made an excellent negative control for the IPMS experiment outlined in example 3. To create this molecule, a cDNA was synthesised with a 5′ EcoRI restriction site, a GCCACC Kozak sequence, the CD33 leader sequence followed by the extracellular domain of human CD83 with a interspaced KpnI restriction site and glycine-glycine-glycine-serine spacer repeated three times (G4Sx3) followed by an additional copy of the extracellular domain of human CD83. This cDNA was then cloned upstream of the hFc6mut in the pJSV002 expression vector previously described. The resulting mature protein is listed as SEQ ID NO: 6 and the tandem CD83 extracellular domain cDNA sequence between EcoR1 and Apa1 is shown as SEQ ID NO: 11.

D.) Construction of pJSV002 NCOMP-hDCIR (SEQ ID NO: 12)

As a negative control for the hTREM-1-COMP pentamer used in example 5, hDCIR-COMP was used. A pJSV002 based expression plasmid was created with the following elements: 6×HIS tag followed by two copies of the streptavidin binding protein domain (SBP) fused to the 3′ end of cartilage oligomeric protein (COMP) such that extracellular domains of type 2 receptors could be cloned 3′ of this fragment as an BgIII/BamHI fragments and expressed as pentameric soluble receptors. A PCR fragment was amplified from a synthetic cDNA template to generate a DNA fragment with BgIII and BamHI ends on the 5′ and 3′ ends respectively. This fragment was cut with BgIII and BamHI restriction enzymes followed by band purification. The resulting fragment was ligated into pJSV002 NCOMP that had been previously cut with BgIII and BamHI. The ligation was electroporated into DH10B E. coli and plated onto ampicillin selection agar. Clones were picked, mini-prepped and screened with EcoRI and BamHI and clones with the proper 1.137 kB insert were sequenced. The cDNA coding for the full open reading frame including NCOMP-SBP and DCIR sequence is designated SEQ ID NO: 12 and codes for the previously referred to mature peptide sequence SEQ ID NO: 4.

E.) Construction of pNNC649-hTREM1-hFc6mut Dimer

TREM1-Fc dimer was used in Example 14 to confirm binding to PGLYRP1 and test binding to other PGLYRP family members. A pTT5 based plasmid (Zhang J et al., Protein Expression and Purification, Vol. 65, Issue 1, May 2009, pp. 77-8) pNNC649 was utilized to allow cloning of extracellular domains of receptors in frame and 5′ of Fc6mut. In order to express hTREM1-Fc6mut, a cDNA was synthesised with a 5′ EcoRI restriction site, a GCCACC Kozak sequence and a hCD33 leader sequence followed by the extracellular domain of human TREM-1 (aa17-200) followed by a Kpn1 site. This cDNA was cloned into pNNC549 using restriction enzyme and DNA ligase techniques familiar to those skilled in the art. The cDNA coding for the full open reading frame including CD33 leader, hTREM1 ECD and Fc6mut sequence is designated SEQ ID NO: 43 and codes for the mature peptide sequence SEQ ID NO: 44.

F.) Construction of pNNC649-hTREML1-Fc6mut Dimer

A synthetic cDNA was created with a 5′ EcoRI restriction site, a GCCACC Kozak sequence and a hCD33 leader sequence followed by the extracellular domain of human TREML1 (aa16-162) followed by a Kpn1 site. This cDNA was cloned into pNNC549 vector previously described using restriction enzyme and DNA ligase techniques familiar to those skilled in the art. The cDNA coding for the full open reading frame including CD33 leader, hTREML1 ECD and Fc6mut sequence is designated SEQ ID NO: 45 and codes for the mature peptide sequence SEQ ID NO: 46.

G.) Construction of pNNC649-hTREML2-Fc6mut Dimer

A synthetic cDNA was created with a 5′ EcoRI restriction site, a GCCACC Kozak sequence and a hCD33 leader sequence followed by the extracellular domain of human TREML2 (aa19-268) followed by a Kpn1 site. This cDNA was cloned into pNNC549 vector previously described using restriction enzyme and DNA ligase techniques familiar to those skilled in the art. The cDNA coding for the full open reading frame including CD33 leader, hTREML2 ECD and Fc6mut sequence is designated SEQ ID NO: 47 and codes for the mature peptide sequence SEQ ID NO: 48.

H.) Construction of pNNC649-hTREM2-Fc6mut Dimer

A synthetic cDNA was created with a 5′ EcoRI restriction site, a GCCACC Kozak sequence and a hCD33 leader sequence followed by the extracellular domain of human TREM2 (aa19-174) followed by a Kpn1 site. This cDNA was cloned into pNNC549 vector previously described using restriction enzyme and DNA ligase techniques familiar to those skilled in the art. The cDNA coding for the full open reading frame including CD33 leader, hTREM2 ECD and Fc6mut sequence is designated SEQ ID NO: 49 and codes for the mature peptide sequence SEQ ID NO: 50.

Example 18: A Multimerised PGLYRP1 Activates TREM-1

A counter-structure or ligand for TREM-1 was identified through binding analysis and IP/MS proteomics. The identity of the ligand, PGLYRP1 (or PGRP-S) was subsequently validated through specific blockage.

Interestingly, while binding of the soluble PGLYRP1 can be demonstrated to the TREM-1, activation of the TREM-1 by PGLYRP1 requires the concurrent presence of a scaffolding agent such as Neutrophil Extracellular Traps (NETs) or PGN.

To test if such alternative, and multimerised formats of PGLYRP1 might bind and/or activate TREM-1, a cell-associated PGLYRP1 protein was designed and expressed. Two conceptually distinct PGLYRP1 constructs were tested. In one, a GPI-anchoring sequence motif was added to the C-terminal end of PGLYRP1. In another, PGLYRP1 was artificially anchored in the cell-membrane through addition, at the N-terminus, of an intracellular (IC) and transmembrane domain (TM) derived from the Type II receptor MDL-1. The latter constructs were denoted Type II PGLYRP1. In Type II 1.0 (SEQ ID NO: 37), the charged amino acid of the native MDL-1 receptor TM is maintained, and efficient expression of this protein, is dependent on co-expression of DAP12. In the Type II 2.0 PGLYRP1 construct (SEQ ID NO: 38), the charged TM residue has been substituted with a neutral amino acid (Lysine to Leucine), enabeling the protein to be expressed independently of eg. DAP12. The cDNAs encoding these constructs were transiently expressed in HEK293 6E cells, cells were harvested on day two post-transfection and analyzed for their ability to stimulate the reporter cell line BWZ/hTREM1. Type II PGLYRP1 transfectants were co-incubated with BWZ/hTREM1 reporter cells in the absence of PGN. TREM1 activation was read out after 18 hours using the BetaGlo reagent (Cat. no. E4720, Promega, Madison Wis., USA). The transfectants expressing Type II PGLYRP1 induced activation of TREM-1 in the absence of PGN, to a level 24-fold higher than seen with control cells transfected with empty expression vector. In contrast, the GPI-anchored PGLYRP1, immobilized via the C-terminus of PGLYRP1, did not mediate any TREM-1 activation. Expression of the membrane-bound and immobilized PGLYRP1 protein at the cell-surface was ascertained by flow cytometry using a polyclonal anti-PGLYRP1 antibody (AF2590). Both proteins, Type II PGLYRP1 and GPI-PGLYRP1, were demonstrated to indeed be cell-surface expressed.

Construct Fold activity C-GPI PGLYRP1 2.0 ± 0.4 (n = 3) Type II 1.0 PGLYRP1  24 ± 3.3 (n = 3)

The table above shows that PGLYRP1 bound to the cell membrane surface via a C-terminal GPI anchor is not as potent in inducing TREM-1 activity as a Type II PGLYRP1 protein bound to the cell membrane via the N-terminal part. This illustrates the importance of a free C-terminal PGLYRP1 part to be able to stimulate TREM-1.

Type II PGLYRP1 activation was further demonstrated to be inhibited specifically by anti-PGLYRP1 antibody. Addition of the polyclonal (Cat. no. AF2590, R&D Systems, Minneapolis Minn., USA) PGLYRP1 antibody at high concentration (1 μg/100 μl assay volume) was thus able to totally inhibit this PGLYRP1 induced activity.

Condition Activity Type II 1.0 PGLYRP1 100% Type II 1.0 PGLYRP1 + Iso Ab  98% Type II 1.0 PGLYRP1 + AF2590  9.7%

Sequences at the very C-terminal domain of PGLYRP1 appear critical to the ability to activate the TREM-1 receptor. Several constructs, which share as a common feature, the modification at the extreme C-terminus of PGLYRP1, have thus been seen to not mediate activation of TREM1/BWZ reporter activity, while the corresponding constructs, which in contrast have been modified at the N-terminus, do exhibit activity.

Construct Activity PGLYRP1 Native +++ PGLYRP1 N-Flag +++ PGLYRP1 C-Flag − PGLYRP1 N-Fc +++ PGLYRP1 C-Fc (+) Type II 1.0 PGLYRP1 +++ PGLYRP1 C-GPI (+)

This indicates the importance of a free C-terminal PGLYRP1 part to be able to stimulate TREM-1.

Interpretation and Biological Perspectives

The ability to activate the TREM-1 receptor using either the native PGLYRP1-ligand in the presence of PGN or alternatively, novel PGLYRP1 variants which have been demonstrated to overcome the need for PGN, clearly demonstrates that PGN is not an absolute co-factor requirement for TREM-1 activation. The common feature of the various molecular PGLYRP1 formats which were demonstrated to confer PGN-independent TREM-1 activation appear to be a high density format leading to the hypothesis that the predominant role of PGN, when acting as co-factor for the native ligand, is to provide a scaffold for multimerisation. In vivo, such a scaffold could be provided by Neutrophil Extracellular Traps (NETs) (Blood 2005, 106: 2551-58) or other naturally occurring matrix structures, such as hyaloronic acid, proteoglycan structures, such as versican, aggrecan, decorin, or fibrin, all of which may multimerise or otherwise present PGLYRP1.

These findings suggest that modification of the C-terminal part of PGLYRP1 reduces TREM-1 activation which in turn indicates that blocking the C-terminal part of PGLYRP1 with an agent, such as an antibody directed against the C-terminal part of PGLYRP1, would decrease the TREM-1 interaction and thereby TREM-1 stimulation.

Example 19: Type II PGLYRP1 is Able to Induce TNFalpha Release in Synovial Tissue Cells from Rheumatoid Arthritis Patients

Synovial tissue samples were obtained from RA patients during total knee replacement. Single suspension of synovial tissue cells was isolated by a digestion via 4 mg/ml of collagenase (Cat. no. 11088793001, Roche, Mannheim, Germany) and 0.1 mg/ml of DNase (Cat. no. 11284932001, Roche, Mannheim, Germany) for 1 h at 37 degree. The synovial tissue cells (1×10^5/well in culture medium RPMI (Cat. no. 22400105, Life Technologies, Carlsbad Calif., USA) +10% FCS (Cat. no. 50115, BioChrom AG, Berlin, Germany) were co-cultured with various doses of HEK cells transiently transfected with type II PGLYRP1 under hypoxic condition. After 24 h incubation, cell supernatants were harvested, and cytokines were measured by TNFa ELISA (Cat. no. DY210, R&D Systems, Minneapolis, Minn., USA).

Type II PGLYRP1 (HEK transfected)/Control TNF-α (pg/ml) release HEK 1 × 10{circumflex over ( )}5 3 × 10{circumflex over ( )}4 1 × 10{circumflex over ( )}4 3 × 10{circumflex over ( )}3 1 × 10{circumflex over ( )}3 0 IgG4 + Type II 121.17 114.08 95.02 54.56 57.87 33.47 IgG4 + Control 55.65 63.73 57.99 33.78 36.40 36.32

This example shows that the TREM-1 ligand can induce TNF-alpha in a dose-dependent manner in synovial tissue cells from rheumatoid arthritis patients.

Example 20: PGLYRP1 Antibodies Block the TREM-1 Mediated Signal in Neutrophils and Decrease IL-8 Release

Having demonstrated that neutrophils can release PGLYRP1 and that neutrophils also express the TREM-1 receptor, we tested whether neutrophil-derived PGLYRP1 can stimulate neutrophils in an autocrine manner. Isolated neutrophils were stimulated with PGN-SA (Cat. no. tlrl-pgnsa, Invivogen, SanDiego Calif., USA), and the release of IL-8 into the culture medium was measured. A PGLYRP1 antibody, mAb 0184, was able to decrease the PGN-SA-induced IL-8 release. Neutrophils were isolated from human healthy donor whole blood as described in example 3 and resuspended in RPMI/10% FBS. The cells were plated out at 1.5×10 E6 cells/ml, and triplicate test wells were tested under the following conditions: no added stimulation, 10 μg/ml PGN-SA only, or 10 μg/ml PGN-SA in the presence of PGLYRP1 antibody or hIgG4 isotype control antibody at 4 μg/ml. The samples were cultured 24 hours in a 37° C., 5% CO₂ incubator. Supernatants were then harvested and analysed for IL-8 using the Bioplex Pro Human Cytokine IL-8 set (Cat. no. 171-B5008M, BioRad, Hercules Calif., USA).

IL-8, pg/ml Neutrophils stimulated with Avg SD No addition 52 3 PGN-SA 1158 341 PGN-SA + isotype control 1195 144 PGN-SA + mAb 0184 449 50

This example illustrates that IL-8 release from neutrophils induced by stimulation with the bacterially derived PGN-SA can be reduced by anti-PGLYRP1 antibody. The TREM-1 ligand PGLYRP1 is thus an autocrine stimulant of neutrophils, and the PGLYRP1 antibody disclosed herein are potentially useful in down-regulating neutrophil responses.

While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will now be apparent to those of ordinary skill in the art. It is, therefore, to be understood that the appended embodiments are intended to cover all such modifications and changes as fall within the true spirit of the invention. 

The invention claimed is:
 1. An isolated antibody capable of binding to Peptidoglycan recognition protein 1 (PGLYRP1) and reducing PGLYRP1-mediated TREM-1 activity, wherein the antibody comprises a CDRH1 sequence as set forth in amino acid residues 31 to 35 of SEQ ID NO: 15, a CDRH2 sequence as set forth in amino acids 50 to 66 of SEQ ID NO: 15, a CDRH3 sequence as set forth in amino acid residues 99 to 108 of SEQ ID NO: 15, a CDRL1 sequence as set forth in amino acid residues 24 to 34 of SEQ ID NO: 16, a CDRL2 sequence as set forth in amino acid residues 51 to 56 of SEQ ID NO: 16, and a CDRL3 sequence as set forth in amino acid residues 89 to 97 of SEQ ID NO:
 16. 2. The antibody of claim 1, wherein the antibody comprises the variable heavy chain of SEQ ID NO: 15 and the variable light chain of SEQ ID NO:
 16. 3. The antibody of claim 1, which comprises a constant region.
 4. The antibody of claim 3, wherein the antibody is IgG1, IgG2, IgG3, or IgG4.
 5. An isolated antibody capable of binding to Peptidoglycan recognition protein 1 (PGLYRP1) and reducing PGLYRP1-mediated TREM-1 activity, wherein the antibody comprises a CDRH1 sequence as set forth in amino acid residues 31 to 35 of SEQ ID NO: 19, a CDRH2 sequence as set forth in amino acids 50 to 66 of SEQ ID NO: 19, a CDRH3 sequence as set forth in amino acid residues 99 to 109 of SEQ ID NO: 19, a CDRL1 sequence as set forth in amino acid residues 24 to 33 of SEQ ID NO: 20, a CDRL2 sequence as set forth in amino acid residues 49 to 55 of SEQ ID NO: 20, and a CDRL3 sequence as set forth in amino acid residues 88 to 96 of SEQ ID NO:
 20. 6. The antibody of claim 5, wherein the antibody comprises the variable heavy chain of SEQ ID NO: 19 and the variable light chain of SEQ ID NO:
 20. 7. The antibody of claim 5, which comprises a constant region.
 8. The antibody of claim 7, wherein the antibody is IgG1, IgG2, IgG3, or IgG4.
 9. An isolated antibody capable of binding to Peptidoglycan recognition protein 1 (PGLYRP1) and reducing PGLYRP1-mediated TREM-1 activity, wherein the antibody comprises a CDRH1 sequence as set forth in amino acid residues 31 to 35 of SEQ ID NO: 23, a CDRH2 sequence as set forth in amino acids 50 to 66 of SEQ ID NO: 23, a CDRH3 sequence as set forth in amino acid residues 99 to 108 of SEQ ID NO: 23, a CDRL1 sequence as set forth in amino acid residues 24 to 33 of SEQ ID NO: 24, a CDRL2 sequence as set forth in amino acid residues 49 to 55 of SEQ ID NO: 24, and a CDRL3 sequence as set forth in amino acid residues 88 to 96 of SEQ ID NO:
 24. 10. The antibody of claim 9, wherein the antibody comprises the variable heavy chain of SEQ ID NO: 23 and the variable light chain of SEQ ID NO:
 24. 11. The antibody of claim 9, which comprises a constant region.
 12. An isolated 1F95 antibody capable of binding to Peptidoglycan recognition protein 1 (PGLYRP1) and reducing PGLYRP1-mediated TREM-1 activity, wherein the antibody comprises a CDRH1 sequence as set forth in amino acid residues 31 to 35 of SEQ ID NO: 27, a CDRH2 sequence as set forth in amino acids 50 to 66 of SEQ ID NO: 27, a CDRH3 sequence as set forth in amino acid residues 99 to 106 of SEQ ID NO: 27, a CDRL1 sequence as set forth in amino acid residues 24 to 33 of SEQ ID NO: 28, a CDRL2 sequence as set forth in amino acid residues 49 to 54 of SEQ ID NO: 28, and a CDRL3 sequence as set forth in amino acid residues 87 to 95 of SEQ ID NO:
 28. 13. The antibody of claim 12, wherein the antibody comprises the variable heavy chain of SEQ ID NO: 27 and the variable light chain of SEQ ID NO:
 28. 14. The antibody of claim 12, which comprises a constant region.
 15. An isolated antibody capable of binding to Peptidoglycan recognition protein 1 (PGLYRP1) and reducing PGLYRP1-mediated TREM-1 activity, wherein the antibody comprises a CDRH1 sequence as set forth in amino acid residues 31 to 35 of SEQ ID NO: 31, a CDRH2 sequence as set forth in amino acids 50 to 66 of SEQ ID NO: 31, a CDRH3 sequence as set forth in amino acid residues 99 to 109 of SEQ ID NO: 31, a CDRL1 sequence as set forth in amino acid residues 24 to 35 of SEQ ID NO: 32, a CDRL2 sequence as set forth in amino acid residues 51 to 57 of SEQ ID NO: 32, and a CDRL3 sequence as set forth in amino acid residues 90 to 98 of SEQ ID NO:
 32. 16. The antibody of claim 15, wherein the antibody comprises the variable heavy chain of SEQ ID NO: 31 and the variable light chain of SEQ ID NO:
 32. 17. The antibody of claim 15, which comprises a constant region.
 18. An isolated antibody capable of binding to Peptidoglycan recognition protein 1 (PGLYRP1)PGLYRP I and reducing PGLYRP1-mediated TREM-1 activity, wherein the antibody comprises a CDRH1 sequence as set forth in amino acid residues 31 to 35 of SEQ ID NO: 35, a CDRH2 sequence as set forth in amino acids 50 to 66 of SEQ ID NO: 35, and a CDRH3 sequence as set forth in amino acid residues 99 to 109 SEQ ID NO: 35, a CDRL1 sequence as set forth in amino acid residues 24 to 34 of SEQ ID NO: 36, a CDRL2 sequence as set forth in amino acid residues 50 to 56 of SEQ ID NO: 36, and a CDRL3 sequence as set forth in amino acid residues 89 to 96 of SEQ ID NO:
 36. 19. The antibody of claim 18, wherein the antibody comprises the variable heavy chain of SEQ ID NO: 35 and the variable light chain of SEQ ID NO:
 36. 20. The antibody of claim 18, which comprises a constant region. 